If there is only one female in the class, she gets her own room. As far as I know, they will NOT pair a male and female together as roommates. Also, I've haven't heard of any problems with people accusing anybody of anything. You may not always get along really well with your roommate but that's the worst of it. I think there is a way to pay for your own room if you want to or can afford to. If your roommate isn't your sim partner, I would think that you will have a lot of time alone - but that's just a guess.