Well whether or not you’re going to be identified is definitely going to be affected by your pronoun preference. If you room with a girl but ask to be referred to by male pronouns then people who know your roommate is a girl are going to know you’re transgender (unless gender neutral housing for freshman is an option on your campus or you can convince them that there was some mistake/issue and a guy was roomed with a girl). If you’re going to go back into the closet and use female pronouns (which I imagine is an awful feeling and I’m sorry that your parents aren’t more supportive) then they’ll probably just assume you’re a butch/masculine girl.
I’m honestly a little torn about whether or not you need to tell the roommate in advance. My first thought was yes because you identify as a man you should say something because the housing is intended to be for two women (especially if your school has a gender neutral option that your roommate chose not to use), but then I started thinking - what if you weren’t actually transgender, but just a really masculine girl. I understand this isn’t an accurate description of how you feel, but in terms of how you affect the roommate, how are you any different from a super butch lesbian (I’m also assuming you’re a heterosexual man), and would I say that a super butch lesbian needed to tell the roommate ahead of time? I would probably say no, you don’t need to tell your roommate ahead of time. So I guess I fall on the side of “you don’t need to tell your roommate ahead of time,” but certainly if you want your roommate to refer to you as a man you’re going to have to tell her at some point.
EDIT: Also “notice” is obviously not the same thing as “care/have a problem with.”