Given the lack of knowledge of the group of these specialised roles (Most people hadn't even played mafia, let alone using special roles), would it be possible for you to post a list of roles, both possible and not. That way everyone gets a chance to read through and familiarise themselves with them. Otherwise I can see the game being over and everyone going 'huh, there's a job that does that? That sucks.' Which will likely spoil their interest in further games. Saying you've narrowed down the list of possible roles from 150 down to 30-50 is a start, but as Reaper says, expecting them to read an entire wiki full of different possible roles and expecting them to understand possible implications doesn't do much to help, and won't help lessen any negative feelings due to a loss/death caused by a role that they didn't properly understand or even realise existed.
Could you at least narrow it down to 10-15? While still a fair amount to read, that would probably reach the line of due diligence for research for the people playing the game.