I'm thinking of eating my roommates' food and not replacing it.
I hope you're joking about that. Are you really going to eat their food?
No I haven't eaten anything yet. But I'm tired of them eating my food.
Well you should discuss that with your roommates. Two wrongs don't make a right and that could just get you into more fights down the road.
I'm too lazy to talk about this with them.
I understand that it is difficult to have these conversations, but this problem will just continue if you don't, and that will cause you more hassle in the long term. Either tell your roommates in person that they shouldn't eat your food, or clearly label your own products. If you eat theirs, you're just setting a precedent that all food in the house is fair game.