I dislike my roommate?

No, you are in the right. It is awkward to talk to other people about things that they are doing wrong so yes, sometimes, notes must be written and posted. It sucks to do, but try to keep your stuff in your own space. Like tissue, paper towels, shampoo, toothpaste, all soaps, and the non-perishable foods. Divide the fridge/freezer in half with some colored tape if you have to and inventory your groceries. It only seems extreme because it will be happening all at once, but hopefully soon she will pick up on the lesson of personal boundaries and you wont have to do all these things anymore.