What can I do if my roommate's boyfriend is living in my apartment?

About three months ago, my roommate asked me if her boyfriend could move in with us. His family was moving out of state, and he did not want to move with them. I said yes because she and I had a close relationship, and I knew she would say yes if I were in her situation. However, since he has moved in, things have been horrible. I found out that he has a criminal background of theft and robbery. He drank a whole bottle of my cough syrup that contained codeine (I had bronchitis and was prescribed it). He and my roommate fight left and right and he is verbally abusive to her. He smokes pot and comes home to my house high, which causes more fights with him and my roommate. At this point, he hates me because I tried to talk to my roommate about this. Now neither one of them will even speak to me or look at me. I feel totally uncomfortable and disrespected in my own home by this man who is not even on the lease or paying rent. There has to be something I can do about this because I know that he cannot stay. I was told that even though he is not on the lease, and he does not pay rent. I still have to contact the leasing office, and they have to give him a 30-day notice. Somehow, this does not seem right to me. Is this the truth or is there a way around this?