So, I'm a pretty scheduled guy on a regular basis. I buy my own food, and eat certain things. And I buy food strictly for my work lunches as well. What is a "professional" way to tell your roommate to stop stealing your food? He won't admit to it. And I have asked him about it before. We agreed on how to split bills. But we each buy our own food. And I've realized he's taking mine and messing up my work lunch flow.