Given the situation, they don't really need to identify the person unless they're charged with something or maybe being investigated for something (if revealing the information doesn't compromise the investigation). Given the nature of the crime and their apparent non-involvement at this time, I'm not sure that information needs to be out there, given the safety concerns that person will be or probably already is facing.
Being a trans roommate is not illegal, there's no threat to public safety, and public interest for the purposes of speculation and bias confirmation (because people are upset that his closest ties at this point are hardline Republicans) is not a valid reason for disclosure. Until they are charged with a crime, they have full rights of a law-abiding private citizen who, because of their roommate, will never live a life of safety ever again.