I am with mattf on this one.
What you are failing to realize is that part of carrying a gun responsibly is making sure you are the only one that has access to it. If you leave the gun somewhere where someone else, like your roommate, can get it, then you are being irresponsible with the gun. Just like giving it to the roommate would be irresponsible.
Now the roommate could always break open your safe with some tools, or ambush you while you had the weapon out. But that has nothing to do with being roommates, that is a criminal committing a crime and it could happen regardless of the circumstances of ownership.
Also, there is no difference between a knife and a gun for the argument you are trying to make. Yeah, it may be easier for you to stop someone with a baseball bat if you are bigger than them. Maybe it is easy for me to stop people with a gun because I'm a 7th degree black belt. Just because you are more willing to confront someone with another weapon doesn't mean that someone using that weapon for violence is not as bad as using a gun.
Anyway, I agree with you for the most part about gun control. I have never really thought about the issue of firearms being allowed on campus, but now that I am thinking about it I do think it should be legal. If I choose to carry a gun to protect myself from crazy people where I live (pretending it is a campus), I don't want that right taken away from me because of where I live.