Keeping your laptop safe in your room is tough...a thief who gets into the room while its empty has more time and privacy to work with. (I went to a college where we all had to have laptops, and there were lots of stories of them being stolen.)
Those cable locks are great for when you're working in the library/cafeteria/coffee house and will occasionally be out of site of the laptop. When you have it in your room I'd just suggest storing it out of site whenever possible -- most thieves seem to look for things left out in the open, and won't rummage around much.
In my experience your major enemy is the college physical-plant crew. They have access to your room whether the door is locked or not. All of the physical-plant workers I met were, at best, less reliable that the average person, and I personally had a number of incidents with them.
Russ