One part powdered (not granular) boric acid (sometimes sold as a roach-killing powder, but often available in pharmacies (for making anti-pinkeye eyewash),
one part white flour, one part granulated white sugar.
The sugar baits it, the flour makes it stick, and the boric acid kills them.
Place in the backs of drawers and cabinets, under refrigerator, stove, etc.
Expect at least 3 cycles of disappearance/reemergence of progressively smaller hordes of cockroaches, lasting about 2 weeks each.
Continue using boric acid till roaches are gone.
****Kids, dogs, and some other pets will eat this mixture. Boric acid is not highly toxic, but is for external use ONLY, so place it where only the bugs can get it. It will cake hard in humid environments, so paper or foil trays may be needed.