If you were going to break my computer, then no matter what locks I have or anything, you could just use a can opener lol.
I think the idea of using your roommates computer is to make it seem like you never did. Now see, if I come home and the front bezel is ripped off of my computer, it would be pretty obvious that someone wanted to use my computer.
I don't even need to have a lock, if the government took my harddrive it would take a million years to figure out what was on it. Everything but boot and my kernel is 2048-bit encrypted, lol.