The best way to get rid of cockroaches is with borax. A one celled animal is a cockroaches bitter enemy as they have the ability to cut open a cockroaches shell, thereby allowing it to dry out, and killing it.
This can be verified by checking out the National Geographic issue that is from Nov/Dec. 1981. It is the copy with the Mt St. Helens pictures on the cover.
I used to live in a place overrun with roaches, this article studying the roaches helped me get rid of them.
Put the Borax/Boric Acid where the roaches will walk through it. Tops of doorways. On plumbing pipes, under cabinets, etc. They will walk through it and carry it someplace where they will roll in it and then die. A roaches other natural enemy is a mouse. If you have a lot of roaches, you probably have mice too. Another thing you can do is to wash off anything that looks like black velvet you find. This is how female roaches impregnate themselves, by walking through this "velvet" left about by male roaches.
Good luck, they are mean buggers to get rid of. But you will have to be careful with the Borax/boric acid around animals and children. DO NOT let kids or animals get hold of it.