I did some asking around and found out the average nature of trolls (I've not played much of the games, nor have I read any of the books, but I plan to). I'm gonna make them a monster race, but someone could bring in a troll that, unlike others, does travel. But since they don't really travel, I'm gonna make them a monster race. Keep in mind that monster race doesn't mean you can't make a character that's a troll. You can play any sentient monster in the game, but you'll have different reactions based on what sort of monster you're playing.

I have found a fifth race that can be a player race, though. Sorcerers would be a separate player race, since not every human can be a magic user. Since magic changes the person, it would be considered a separate race, just as Witchers are considered separate.