Photoshop your roommate into a wanted poster like this: http://www.localmugshots.net/WantedP...op_463x600.jpg
...and post it all around campus the night before April 1st. Make sure It looks legit.
The next morning as your roommate is going to class, he'll have people chasing after him, and trying to tackle him. Eventually he'll spend the afternoon at the police station.
But you have to make sure your poster looks realistic. Also, I'll work better if your roommate looks like a thug, which mine does.