Your roommate posted a note above the sink that read, "Please wash your dish after you use it. I saw a roach!"
Do your dish, then post your own note that reads, "I don't even live here. I sneak in during the day to have lunch and get warm. I also sometimes put on some of your clothes, then walk around the apartment shouting Ooooh look at me I'm one of those hot babes who live here. Aren't I housed! Look at me! Then I write a poem in very small print someplace on your walls. I can't believe you guys have roaches now. I've hated it here. It's drafty. But now I have to put up with bugs? Fuck. Anyway, I did my dish. Just trying to pitch in. Also, I saw you cry late last night while you were on the phone. You drank two great big glasses or wine. Are you okay?"
When your roommate gets home, she'll read your note and call the police. When the policeman comes into your room to interview you about the intruder, tell him that just between you and him, there was no intruder. You posted that note because your roommate's such a priss. The policeman will say, "I kinda got that sense."
Happy Please Wash Your Dish After You Use It Day!