Those who've encountered them will probably be familiar with their chirping sound, often leading to sleepless nights. Roaches have ridges on their legs to help them move around on uneven surfaces.
They can be identified by how many of these ridges they have; German roaches, for example, typically have two of these, but Oriental cockroaches will only have one ridge instead. They also shed their skin, but unlike most insects that tend to molt a single time during development, cockroaches may molt up to 15 times over a lifetime!