college roommates are like prisoners. beat the shit out of someone the first day, or become somebody's bitch.
But really, it isn't that bad. Even if you get stuck with someone you don't really like...it'll actually help you make more friends. I didn't like either of mine too much (forced triple) so since i tried to stay out of there often, i ended up meeting a bunch of cool people and found 2 great guys to room with next year, and we all get along flawlessly.
or if you have a feeling you won't get along...just don't talk. I did that with one of mine as well. We knew we wouldn't get along well, so we talked minimally so we wouldn't find out more about each other to not like. As a result we got along just fine.