Many years ago, CHOICE recommended Dead End cockroach mats. They're no longer available in supermarkets, but if you search online, you can still order them.
They are a cardboard mat with a non-sticky coating. The roaches pick up the insecticide from the mat as they walk over it. We've found them very effective, and if you vacuum off any dust that accumulates, they keep working beyond the claimed three months. You can slide them under things like fridges, or use a little Blu Tak to keep them anchored in the corners of cupboards etc.