On good authority, but I hear it's mainly a 'guy thing' (guys don't cover microwave dishes): scrape all the debris from the ceiling of the microwave.
Now, in a woman's kitchen... many of us answer the question "Is the pasta cooked enough?" by flinging a forkful at the wall behind the stove; if it sticks, it's done, if it falls, it's not. Pull out the stove and scrape up the remains (still needs cooking).
If you can eat cockroaches, you can probably check out all those Tupperware containers on the bottom shelf of the fridge, way in the back. Shake them a little, and if you get a response (tiny cries, scratching, etc), it has evolved to a higher life form, and can probably be killed and eaten.
Sue