Cockroaches come in many varieties, most of which live outdoors and play their part in the general ecology of your garden and rarely venture indoors. Some live in your roof void or subfloor, and rarely venture into your dwelling space. Some however are notable pest species. They include the American cockroach, the brown banded cockroach and the German cockroach, the latter being the smallest, but most prolific breeder and arguably the hardest to eradicate.
However, thanks to modern chemical technology we can usually fix even a bad problem in a couple of treatments.