If you haven't already, you should report him ASAP, so that if he succeeds your university will know he copied you and not the other way around. A record of you having lodged a complaint first would make your story more credible if it came to it.

Report him for plagiarism and do it immediately. Otherwise, you could be the one that comes off looking like a thief, and gets kicked out as a result. And getting booted out of a program due to plagiarism accusations makes it near impossible to get into another school.

You want a time out? You better spit a rhyme out Before the community of real mc's die out College students say to me "you ain't smart" Record label A&Rs say: "this ain't art" These are the contents of the covenant of the art Listen to my chest beat tell me this ain't heart You gotta be as obsequious As the Disciples of Jesus This is my MASTER THESIS

Sounds like the kinda relationship you'd normally have with your parents

Report him to your professors for plagiarism. Then slam his fingers in the desk drawer.

To be fair, I read and used the theses of 4 former students from my lab to help me with layout and finding sources for my thesis. Given the fact that no master's thesis is on the exact same topic, I highly doubt your ex roommate would be able to copy it (I can't imagine your advisors approving the same topic, especially not in the same program at the same school). The FML here is the fact that someone was going through your shit, which is not acceptable at all.