As a parent I would agree with this. I would have no issue with any of my kids rooming with someone that is gay, trans, opposite sex, different race, religion or straight haha. But many are not as open minded and would so why should you have to be anxious about it right from the get go? You are also not the only kid going through this right now. If you don’t match with a roommate beforehand most schools have roommate questionnaires they have you fill out beforehand and you can probably put that out there. The benefit in it is having someone who is not homophobic or intolerant. Also it’s no different than when you put a preference that you don’t want a smoker or early riser. The only issue I see is that you want to make it clear that just because you’re gay it doesn’t mean you’re looking for a gay roommate unless of course you are.
Congrats!