Sprays are easy and fast to apply. The spray should wet or dampen the treated surface, but not puddle. Spray cracks and crevices where cockroaches hide. Dusts are applied in crevices and cracks, under refrigerators and around sinks and cabinets. Apply dust insecticide lightly, where it is barely visible.
Boric acid is one inexpensive insecticide for cockroaches.
It is low in toxicity for humans and pets and is available at drugstores and hardware stores. Apply in a light film to cracks, crevices and under and around heavy appliances. Do not apply to cabinet and shelves. Avoid storing paper bags, cardboard or newspapers in or near the kitchen. These are hiding places for cockroaches.