Cockroaches will eat any kind of organic material, they may eat (rotten) onions if that's what you meant.
what does the cockroach eat
my head
they eat small poppys
they eat carrots
Bread
bananas
Meat
It has an exoskeleton.
Exoskeleton.
Omnivores can eat all kinds of plant, as long as it is not poisonous to their system, such as the leaves of the potato plant.
If you eat a cockroach, it will die and you will digest it. It will turn into food. The exoskeleton will eventually be eliminated in the toilet.