Always roast in a metal tin, this will conduct the heat better. Never roast the spuds in the same tin if you want crispy spuds, do them separately in hot oil.
This is how I make my roast beef:
In the roasting tin place
2 carrots roughly chopped
2 onions roughly chopped with skins on
1 head of garlic, broken into cloves (unpeeled)
3 tbsp olive oil
season with salt and pepper.
Brown the meat on all sides and place on top of the vegetables. Roast for the calculated time, remove the meat and allow to rest wrapped in foil in a warm place.
Now’s the time to make the gravy. Prepare about 500ml. of beef stock, I use those Knorr jelly thingies.
Put the roasting tin on the hob over a medium heat. Use a potato masher or wooden spoon to bash all the vegetables, which will now be soft and slightly caramelised, into a pulp.
Pour in the stock. Bring to simmering point, stirring and scraping hard to lift all the brown gunk from the bottom of the pan.
Pour this dark looking mess through a sieve into a bowl (or use a gravy separator), pressing well on the solids to get all the juices out. Throw away the solids.
Spoon the fat off the liquid and put a couple of tablespoons of fat back in the roasting tin. Add about 1 Tbsp. plain flour and cook until brown and nutty smelling.
Add the dark liquid to the flour mixture and cook, stirring, until smooth, thick and glossy.
Add any juices that have gathered under the resting beef (they have a wonderfully beefy flavour) and taste to check the seasoning.
Carve the beef and serve with the gravy.