1. Approach the roommate in the least threatening manner to discuss the issues you have. Remember, don't be condescending. That's offensive and most people don't like to be talked down to.
2. After addressing the issues with your roommate and no changes have occurred, inform your RA (residential advisor). They can give you advice and possibly mediate an argument to help you find a happy medium.
3. If things still haven't gotten better and you hate being in the room the same time as your roommate or whenever you see them you want to beat the crap out of them, it's best to alert the RD (resident director) or housing.
4. The best thing you can do at this point is to move out (or maybe if your roommate doesn't like you either and wants to go somewhere else, they can move to another dorm).
Hopefully this is helpful. Just remember to be calm, cool, and collected and don't be an asshole towards them. That can only make the situation worse. Plus, you don't know if your roommate is psychotic and will do things to you....i'm just putting that out there because ish like that happens. lol