There are many species of cockroaches, most of which aren’t pests to humanity. Just living their little bug lives out in the wilderness munching stuff. And getting eaten by insectivores in large quantities.

Humans wouldn’t notice much at first, but things would seem off and get worse over time. Disappearing animals - birds, reptiles, fish. Angry frog owners pacing back and forth. Orkin men begging in the streets.