Oh boy, I could say quite a bit on this. Where to start?
First off dude, there is a lot of good info and advice in this thread. Head it wisely.
What I would do...sleep naked with no covers yourself...just because it feels good to sleep naked. See what happens....
^this
I have been on many all-male sports teams and all of the guys I basically grew up with are straight, so trust me when I say this: that's just what straight guys do

And only us - the gay guys - will notice that they put a hand in their pants and start playing with their balls

Thats just how most of them are. Same with showing off their dicks

If a guy has something to show, you will probably see it at some point

It's just showing that they feel comfortable. Hell, I'm gay, but act the same way around them, cuz that just how it always was and probably will be.
.....
If, and thats a BIG if IMO, he makes a move then you can think what to do about it, but for now I would just enjoy the views and not think about it much. Think about it this way: it may actually help you - you will get used to see guys naked and when you have a boyfriend you will feel more comfortable taking your own clothes off from the get go
^ and this.
I'm coming from the perspective of your roomie.
I am a nudist and very much a "man's man" type of dude.
You would hate me as a roommate.
Because I would be naked all the time and jo around you, piss and shit with the door open and if you didn't reciprocate, it would weird me the fuck out.
Even though I never had brothers, I'm a military brat who grew up with two large sets of buddies who were brothers (6 brothers in each set) and included me in with their respective"packs". I also played sports growing up and I've had male roommates off and on for several years now.
Question for you.
You said he didn't do these things before you came out to him, but started soon after.
Seeing as how school just started for most college kids only about a few weeks ago, how long are we talking here where he didn't do these things before your big reveal?
Last year when I moved into a dorm-like complex for college students, it took at least a couple weeks for the roomie and I to become comfortable with each other before we could be ourselves around each other. I was fortunate to discover he was a fellow nudist who eventually joined in on occasion to the open jo sessions. He was also straight, only 19 and had a girlfriend. Interestingly, he initiated much of the nudity and jo sessions himself and I was constantly catching him checking me out, sometimes blatantly staring at my junk, so I returned the favor and even complimented him a couple times....he had a nice cock. We eventually bonded to where he felt like a little brother to me, but his school year was up in August and he decided to take a year off and move in with his girl, so now he is missed.
My point.
It may have taken a few weeks for him to be comfortable to be himself around you.
Wanting to bond with other dudes to feel accepted, inclusive and seeking "approval" from someone you like, respect and admire doesn't always mean there is a hidden agenda of wanting sex from you. Even though the things he does to him are normal but to you are awkward, absurd and inappropriate.
It sounds like you both grew up differently, like, polar opposites of each other.
If you're not willing to either join in on the whole nudity and open jo sessions or at least let it go and not let it bother you, all you can do is request to be paired with someone more conducive to your social sensitivities.
Just remember though, the whole point of college is to help you gradually become exposed to the larger world, to help you come out of your shell. You will have to stop hiding at some point.