My roommate barely speaks to me. He brings girls in to spend the night and throws condoms on the floor. What should I do?

Talk to him. There is nothing more frustrating when a roommate is disrespectful about living quarters (and the throwing condoms on the floor... Who does that?!) you won't get peace until you politely but firmly ask him not to do it. His behavior won't change magically by itself, and you'll just get more and more frustrated if you don't bring it up. If he doesn't respect your wishes, time for a new roommate.