Alright, so I think there are several things you could do in this situation to try and relieve some of your dysphoria and also help you figure out what you want exactly.
1) Do you have your own private room in the place you share? If so, you can just keep the stuff hidden in your room and dress up on your own when they aren't around or if you can lock your door do that. If you share a room with someone else, then you would need to know for certain that they wouldn't be around to catch you.
2) If that's not a possibility for some reason, do these guys seem like the accepting type? Have you guys been good friends for a while, or is it simply roommates type of thing?
3) Do you have any close girlfriends? I understand you don't want to come out completely but if you know someone you really trust, you could always be honest with them and tell them you aren't 100% sure and you just want to experiment essentially. If so, maybe consider "coming out" to one of them that you trust and tell her your dilemma. My guess if you do that, then she would be more than likely willing to help you dress up like a girl. (I say this from my own experience).
4) If some reason none of those options work at all, then you may have to wait until your lease with them expires and then reconsider your living situation because it does matter for both privacy and safety. I had a roommate in the same room and I had to be extremely careful, so I understand how frustrating this can be.
I don't know if any of this can help, but my strongest recommendation would be to confide in a girlfriend that you really really trust and that would be a good outlet for you to start I would think, but this is just what I would do if I was in that situation and it is what I did when I was there. I'm also a college student, so I understand the dilemma of telling college guys and the fear that comes with that. I wish you the best of luck and don't be afraid to ask more questions, we all want to help!
Emma