I would recommend you do the same thing my freshman roommate did the first day or two of moving in. He informed me he was gay, and we had a conversation about the ground rules of living together (which is something all roommates should have). I did not have a problem with it and we got along well. He ended up moving off campus after one semester, and, as far as I can tell, he didn’t have any issues in the dorm with his sexual orientation even though it was well known. This was 30 years ago BTW.
In any case, it is relatively easy to change roommates in the first week of a semester as there are always people looking for a change. After the first week, it becomes more difficult. Just be upfront about what you expect from a roommate, and don’t be judgmental about him.
Good luck!!!