I was talking to my D2 (college junior) about this today, and she commented that pretty much this exact situation occurred during her freshman year with a friend & the friend’s roommate. She said it was just no big deal – says her friend is “chill”, and it really wasn’t an issue. The trans roommate started passing as male partway through the year, and now lives in a single. D2 thought it would be best to meet the roommate and get to know them a bit before telling them.