1) Hydraulic assisted bolt cutters, not too expensive and yes I have some.
2) Kill switches can be a pain to figure out, but if I got physical access I can take my time. Eventually I will figure it out. Plus there are manual ways to trigger a PSU, which I have done before.
3) Reset the BIOS once the lock is broken.
4) Encrypting your hard drive is almost fool proof, that would stop me in my tracks.
Now, to say that a roommate would go as far as to use bolt cutters on your lock is kind of messed up, and you probably shouldn't live with someone like that anyway.
However, my main point wasn't about if someone would do that as a roommate, my point is, someone could do all of that if they wanted to.