I had a similar issue while in college. Rather than immediately going to the school, the first thing I did was talk to my roommate about my issue with him and his friends smoking in the room. He and his friends did make some effort, such as putting a towel under the door to try to minimize the smoke going in to my area, but it was not enough. It didn’t seem that we were going to be able to resolve the situation.
My next step was going to the admin that handles the room assignments. I didn’t mention the smoking weed, nor did I need to give a lot of details. If I remember correctly, I mentioned something about not getting along well and asking if there were other available rooms. She said there were 3 persons in the dorm with no roommate (likely due to their roommate leaving during during first quarter), and I could switch to any of the 3 available rooms.
I talked to all 3 of the of the students with available rooms to see who I thought I’d get along with. I mentioned my problems with the other roommate smoking when talking to the students. After hearing this, one of them showed me his bong and talked about how much he liked to smoke, so he was off the list. However, I did find another student who I seemed more compatible with and switched rooms. It was a simple move since I was going to a room within the same dorm.
I stayed the rest of the year with the new room and roommate, without issue. I got along better with him than any of my other roommates, even though on paper we were nothing alike, aside from both having a high tolerance for messiness. There also was no retribution or negative issue with my old roommate and his friends. We said hi when we ran in to each other at the gym, but otherwise remained uninvolved with each other, after the move.