So, here's a quick rundown of the possible characters that could be in the game, in alphabetical order:
Backup - As the name suggests, they are a backup to replace a townie role that dies. For instance if the cop dies, the backup cop will become the cop. It's up to the GM if the backup gains the knowledge that the person they are replacing knew (investigation results, for example).
Not useful until the role they are backup to dies, but good to ensure that if the role gets lynched or killed in the first day/night the townies don't have a massive disadvantage.
Bodyguard - Can target a player at night to protect them. If they would have been killed, the bodyguard dies instead. The only real use for this is if the cop reveals themselves and knows there is a bodyguard, which allows them to reveal their investigations and the bodyguard can let them get one more investigation off. A worse version of the doctor (see below). As a bodyguard you still want to protect someone every night even if you don't know who the cop is, simply because you will stop someone potentially more important than you from dying. Of course you don't know what role they are for sure, but there's a chance you'll save someone who can gather information, so you should always block.
Bulletproof - There isn't too much to go on with this. Being bulletproof means you can't be killed at night, and as such is very powerful. Sometimes this is simply limited to a one use protection, so once you get night targeted once, the second time will kill you.
If you're a townie, then you want to do things to draw scum suspicion towards you since then their attempt at killing you will fail and that's one night wasted for them, while any townie people can investigate freely.
Bus Driver - The bus driver picks two players at night, any person targeting player A instead targets player B, and vice versa. This will alter things like night kills, investigations, everything. If a cop investigates, they generally won't be told that they ended up investigating someone else.
This obviously creates a lot of chaos. While it could mean that you can redirect mafia kills onto other people, potentially other mafia members, you can also screw up your cop investigations, assuming there is a cop. A dangerous role.
Commuter - Has the ability to leave town completely. This is another one that depends on the GM, they can either do it every night, every other night, or only a certain number of times, with the Commuter deciding when to use the power. A very powerful role since obviously it means you are immune on whichever nights you are commuting. This is similar to bulletproof, but with subtle interaction differences. Bulletproof is simply immune from night kills, the commuter isn't affected by anything. No investigations, no nothing. They aren't there!
Cop - Come on, you should know this by now!
Deflector - Similar to a bus driver, except instead of swapping the actions between the two players, you direct actions from player A to player B. Player B thus becomes the target of everything targeted at bother player A and B. If there is a deflector and a cop, the deflector can render the cop invulnerable by targeting them every night. Then the only way to kill the cop would be to kill the deflector first.
Deputy - The same as a Backup Cop. If the cop dies, the deputy becomes the cop.
Doctor - Kinda redundant given the theme of the game.
Doctor - Targets a player each night and gives them protection from a single kill that night. Obviously very powerful, and as with the deflector you can keep a cop alive for a long time.
Fisherman - A weird random luck role. You are given a list of items and a percentage chance of catching each one. At night you select a certain item and will fish for it, having that percentage chance of finding it. Each item is one use, can only be fished up once, and can be used any time. Items can let you: Investigate, kill a player, be a one shot doctor, tracker or watcher.
Incredibly luck based, may not even fish a single item up. What you should go for depends on the percentages and game situation. Good luck!
Flavour Cop - Rather than being told if someone is townie or mafia, they get a clue towards their actual role. For instance, they could be told someone is medical, indicating they are the doctor, or a similar class. The way this is reported depends on the GM, some simply give clues towards the flavour, others state it outright.
This can in some ways be more important than a regular cop, since if you're a cop and seeing that there is a townie being lynched, you don't know if they are worth saving. Howeve if you investigated them as the flavour cop and discovered they were a really useful role, you may do something more drastic to save such an important role.
Follower - You follow a certain player and discover what (if any) action they did that night, though it doesn't say who on. For instance, you could see if they investigated someone, tried to protect them, kill them, etc). Pretty similar to the flavour cop.
Friendly Neighbour - You tell another player at night that you are a townie. Pretty useful because knowing people who are innocent for certain gives you higher odds of lynching scum. You don't want to tell a scum player who you are though, since someone who is a guaranteed townie is bad for them for the above reason.
Godfather - The first one so far that's a scum role. When investigated by a regular cop, the Godfather shows up as being a townie. He works as scum in every other way.
Innocent Child - Not in this game. Would be announced as a townie at the very beginning of the game.
Inventor - A variation on the fisherman, except the inventor starts with lots of inventions and may give them out to other players. Some variations, such as the abilities the give out being randomly decided by the GM.
Jailkeeper - Locks a player up overnight. The target is basically put in jail overnight. They can't be killed, but they can't carry out any actions either. Kind of useful, but because you stop a target carrying out their actions, you don't really want to use it on a cop unless you know they will be targeted that night. Potentially lets you stop the mafia killing someone by jailing the one who would carry out the kill.
(Ok, this is taking longer than I thought)
Janitor - Janitors are part of the scum team, and usually have a limited number of uses. When the janitor uses their power, the player killed by the scum that night only has their allignment revealed, rather than an actual role. This of course assumes that the GM is revealing roles on death. If not then this won't be present.
Lightning Rod - They just attract so much bad stuff! Either permanent or limited number of uses, the lightning rod attracts all night actions. Good and bad. This will generally mean nothing happens assuming that there is one night kill and one person who can protect/save. Except investigators will also investigate the lightning rod rather than their target, without knowing.
Lynchproof - The clue's in the name. If they get lynched, they survive, though it's generally one shot, and often combined with a second power. Good for whoever is it.
Mason - No idea if these are in the game as Jedit also said they were too complicated. There are lots of variations, but generally masons are a group of townies who know who each other are, and are allowed to communicate privately in the same way the scum do. This may be limited to purely day or night though. Probably not in the game though.
Neighbour - Neighbours are similar to masons, except not necessarily all town. There is usually one scum and 2-3 townies, but not always. Could be decided randomly or could be set up to be a certain ratio, up to the GM.
Ninja - Another scum role, and similar to the Godfather. Except instead of appearing as a townie, if one of the searching roles lookes at them (like tracker or watcher) rather than being shown as having targeted someone, they look like they did nothing.
Oracle - The oracle is able to ask the GM about the game set up. For instance asking the number of scum players at the start, if there is a certain role. You can't ask who, the information is limited purely to roles present at the start of the game. Pretty useful, though given the number of possible roles, odds are you won't get much useful info. Number of starting scum players is about the most useful thing you can get.
Priest - The priest can't cast the final vote which will lead to someone being killed. Not much use for the town, will just be a distraction since they will never land the last vote, which can possibly be seen as scummy.
Redirector - Similar to the deflector, however rather than bouncing everything off a single player, you pick someone and any action they perform that night targets a player of your choice instead. Again, this can screw up investigations, but you could also make a night kill target a scum player instead.
Reporter - Investigates another players house to see if they are at home that night or not. This doesn't actually reveal this much since being targeted by someone and targeting someone both take you out of your house, and with lots of different roles, this probably won't reveal anything of value.
Role Cop - This will reveal the role of the player in the theme. In your initial role email it will contain your role. I can't go into much detail on this since I don't know how all the emails look. But it will give you a rough idea of the sort of role the target has, without actually saying what the role or alignment is.
Roleblocker - You target someone, and that night thye can't perform any action. This is usually a scum role since you can stop a doctor or cop from protecting or investigating.
Rolestopper - Like an upgraded jailkeeper. You protect someone from all night actions hitting them, but they can still carry out their night action. Sometimes these can't protect against nightkills, making the role a bad one since you stop the cops finding out that you're good.
Strongman - Often one or limited uses, when the strongman tries to nightkill someone, it happens. Jailkeepers, doctors, none of these can stop it. A powerful scum role, though being limited uses means they can't just steamroll through everyone.
Survivor - One of the few third parts roles, the survivor is neither town or scum, they simply win if they are alive at the end. No other abilities to help them, not that useful to the town either.
Switch - A weird role, a switch can enable or disable certain roles (Commonly used on vigilantes). Switching them off prevents that action from being used at night, switching on allows it. Possibly useful if there's a bus driver who would cause confusion, but not much help really.
Tracker - You follow a player at night and learn who they targeted, if anyone. With a lot of possible night actions, this can be somewhat limiting, but generally if you track someone and they target the person who died, there's a good chance they are mafia. Or they could be an unlucky cop who targeted the same person.
Traitor - A scum player, though the exact rules vary with the GM. He is always unable to talk with the other mafia, and can't carry out the night kill. May or may not know all of the scum players, usually have one of the other abilities that helps the scum out to keep them useful.
Tree Stump - Another very weird role. When a player becomes a tree stump, they can still post in the thread, but do nothing else. No abilities, no voting, no dying. They are essentially dead, just able to keep posting. It's up to the GM how a player becomes a stump. Sometimes they have a role which just lets them become a stump at night, others may have it happen if they die.
Universal Backup - Similar to the backup right up there at the top of this post, except rather than being a backup for a specific role, the universal backup will replace the first townie role that dies.
Vigilante - Extremely powerful, though usually with a limited number of uses, the vigilante is a townie who can kill at night. These kills appear the same as scum kills, but obviously are done by a townie player aiming to kill a scum player. Sometimes they can kill during the day or night. Either way, you want to save your shots until you are pretty certain that a player is scum, otherwise you are bringing them closer to victory.
Visitor - Yet another weird one, Visitors just get in the way. They can target another player at night, but they don't actually do anything. They don't discover anything, and just get in the way of investigations.
Voteless - Self explanatory. You can't vote, which makes you extremely useless since voting is the key way to kill scum. There's a chance scum will claim to be voteless as a reason for them not voting.
Voyeur - Not as fun as it sounds, the voyeur watches a player at night and discovers what happened to them (Investigated, protected, etc), but not who did that action. Generally pretty useless, about the only thing to look out for as this is if you happen to see someone being investigated. You can then watch how players react to that person the next day and potentially figure out who the cop is.
Watcher - Final one! Watchers watch someone, and they can see who targeted that player that night. If you're the watcher you should watch who you think the scum are most likely to target. If they die, you know that one of the people (Assuming other roles were targeted at them for the same reason) is scum.
