I'm bothered by my sober house roommate
Why are you bothered by your sober housemate?
He has been eating my food for a long time
There is no reason he should be eating your food without your permission because it's inappropriate behavior. You should talk to him about it and make sure he knows how serious you are about this. Otherwise, he will just keep eating your food.
I will have a talk with him this evening.
It is good to do things like this in a nonconfrontational way face to face. Maybe it is a misunderstanding and your roommate did not know what he was doing.