Simple bait or poison, specifically for cockroaches can be bought from hardware or gardening stores.
Once the cockroach infestation is gone, a repellent can also be purchased which creates an 'uncomfortable' living area for the cockroaches, warding them off an preventing another infestation.
They must be cleaned out from wherever their nests (there are usually many) are. If possible, seal off the places you have cleaned, but, first, fill the spot with boric acid powder. I have used calking, spray foam, and liquid nail to seal off these spots. It seems that almost anything will do. This powder is the best deterrent to cockroaches that money can buy. Make sure that you do not inhale the powder, and don't let children and pets get into it. It can be purchased at a low price at Dollar General and Family Dollar. Most hardware stores have it, too, and any big chain department store should have it. Good luck.