My roommate, or people my roommate's friends are stealing things.

I had an entire DVD collection taken from my apartment (they were in 2 giant DVD wallets), a Wii, and a towel rack go missing over the past couple of months. My other roommate had her digitial camera go missing. I asked the roommate in question if his friends went into my bathroom since they had been over the night it went missing. He said no. Later I noticed all my DVDs were gone, I asked if he had seen them, no again. And while I was gone over the break, he kicked and broke my door (not all the way, my other roommate stopped him). The only thing I have proof of is the door. Is there any sort of threat I can place on him to get his friends to return the stuff?