My roommate [21M] keeps jacking up thermostat further, making me [21M] uncomfortable.

Hi!
So I moved into my apartment at my university about 3 weeks ago. Where I live, we have very hot summers. The past three weeks have been around 95 degrees and higher sometimes.
The AC in our rooms has no return air so hot air can't be sucked out, and only cold air is pushed in via vent. This means without the AC running low it can get pretty hot fast, especially with the bedroom door closed. I lived in the same complex, different apartment last year and it was never a problem with the AC because we just kept it at 68 degrees.
Disclaimer before continuing, utilities are included in our rent bill, so setting the AC at lowest possible or off entirely doesn't cost us any more or less, so we effectively can do whatever we please AC wise with no cost
However, this year it is a problem. When I moved in I set the temp at 68 and my roommate was like awesome. The next day when my other roommate moves in he sets it to 76 degrees. I start sweating in my room since it probably has gotten to over 80 (because the lack of air flow, hot air accumulating), and ask if it is ok to set it at like 72. He agrees. Even at 72, my room is still warm, a little annoying but a comprise. With a fan it's manageable.
This is when the roommate gets on my nerves. Over the last week, he has actually shut the AC off entirely at night or it turned it up further. One time it got to 78 by the thermostat, probably nearing 85 in my room. Just unbearable. Waking up in sweat. My girlfriend was over and just turned it back down to 69, and literally like an hour later he moves it back to 72.
I haven't said anything since the initial confrontation, mainly because I am non-confrontational and would like my roommates to like me. It isn't the world's biggest deal, since temps are dropping and in a month or so opening the window will solve the issue until spring, but I would also like to be comfortable in my own room with my door closed without sweating. Also my thought process is that if its cold you can put on a sweatshirt, but when its hot I can't really do anything except a fan and that only goes so far. I am wondering if I should just kind of deal with what the thermostat master brings me or should I try talking with him? If so, how should I hand this situation?

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tl;dr: Roommate keeps turning AC for no reason, and its making me miserably hot.


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