Most guys in dorms and roommate situations never say a word about masturbation and have to do it surreptitiously when their roommates aren't around or learn to do it in the shower or toilet. Is this common or am I an unusual type guy? We have a rule that we don't do anything involving our genitals. I told her it this was something I do to myself quite a bit, and that it was very special to be able to share it with her. I froze at first, then just walked into the bedroom chuckling.
As you state, everyone knows that both he and his roommate masturbate in the dorm room, so all you really had to do was ask to be alone and he would have understood what you were going to do. I enjoyed masturbating regularly through high school. Such a waste.