Hi, I’m straight, and the first and only roommate I ever had in dorms was GAY. So, although I’m not gay, you could take my thoughts/story on this.
This is all in my opinion, but you should 100% come out and say it at the start, though perhaps after their parents are gone as it might get a little awkward lol. But before you do that, I highly suggest you look for roommates. Almost every real college has that option, same with some apartment complexes geared towards students. Look for roommates, and put it in your description too. Finding a good roommate that you match with is sooooo important. I honestly got lucky with the auto assigned roomate I got as I could’ve gotten people way worse. Like I’m litrally happy that I didn’t get a roomate that was obnoxiously loud, a druggy, stays up super late, inconsiderate, and is a general messy person. But there was still a big problem that I had with him… It was that dude literally jacked off every night in his bed when he thought I already fell asleep, after a certain point the guy didn’t care anymore. Whatever you do, please don’t jack off to your roommate… and you’ll be fine… like please don’t…
I guess my roommate got lucky getting me cause I honestly didn’t care about him being gay as long as he didn’t do gay stuff towards me… Other than that one part though… I honestly liked him as a roommate due to him having a bunch of good qualities that could’ve been a lot worse with another roommate.
I really suggest you just say it out though. Some people really hate people who aren’t straight, others might be a little uncomfortable, others won’t care. If you have someone you know right away that you two will have problems, you can switch your roommates most likely. Talk to your floor manager or request help and they’ll likely do something about it unless you wait way too late where there’s no other options… But it is much better for them to know right away than to come to know later on.
If you have the ability to still though, try to find your own roommates as this much much much better option.