I am also a college student and have seen how this situation can progress (fortunately not to me) and the consequences that can happen to the innocent roommates. I am happy that you are starting to get somewhere with the campus authorities although I have a few recommendations.
BEFORE YOU DO ANYTHING ELSE! You need to search everything thing that either you own, have partial ownership or is considered to be in your possession. Desks, drawers, bags, fridges, even your clothing pockets. From what I have seen the type of person you are dealing with will have no problem storing their illegal belongings in areas that could put you in hot water. I have watched friends loose their college scholarships and education over some druggy hiding their stash in their roommates belongings. You want to be absolutely certain that anything that has your name tied to it has nothing within it that could tie you to the drugs. Even search dirty crusty socks that have fallen behind furniture and do not take his word for it!
This is something that you are going to have to do constantly. If you have a car or a friend in another dorm or house that you can store some of you stuff in securely I would highly recommend that. Especially if this guy starts dealing before you are able to move out, he is going to have more illegal substances that he will need to find "extra" hiding places for.
If you are able to find someone who you can stay with either a couple nights a week or more that can be very beneficial. As people have said you need to separate yourself as much as possible from your roommate and that dorm room.
Document everything you have done and everything you do in trying to resolve this problem.
I know this sounds a bit extreme but unfortunately if the police do get drug into this or even if it is just the school itself, from what I have personally seen happen to other people, more cases then not, you will be guilty until proven innocent.
I know that it is not very easy to just up and move out of your dorm, and more likely then not, you are going to have to wait until after winter break to get a new room because the higher-ups tend to not take these things with much urgency.
Until then, separate yourself as much as you can even if you have to sleep in the common room.
Hopefully your experience will not end poorly, but you need to protect yourself.
Welcome to College