You know, the roommate might have killed him...planted a bomb in his monitor and rigged it to go off while he was "taking a bath". Maybe the guy was ripping off him off, stealing his codes...so he had to do something about it.
Him, being some crazy tech genius, looked on google how to make a bomb and a detonator. Then he carefully planted the bomb in his roommate's computer, awaiting the arrival of said roommate. As soon as he got home, he stated he was "going to take a bath", making sure to bring the detonator with him.
He waits a few minutes, peaks out to check that his roommate is indeed in front of his computer, and then...he activates the bomb. When police arrive, he claims that he ran out and "fainted". Hmmm, sounds fishy. Who faints these days, I mean, be realistic. Just some food for thought.