Cockroaches live inside cardboard and paper bags and can eat the glue that binds them together. Do not store boxes, cardboard, equipment paper, clothes, or containers on the floor, and don't wedge paper bags between appliances or inside cabinets. Replace wooden shelving with plastic or stainless steel, or caulk gaps between pieces of wood shelving, after cleaning and vacuuming. Try to keep shelves 12 inches off the floor and 8 inches away from walls so you can inspect them easily from behind. Eliminate clutter, especially on the floor or in cabinets under sinks.
Cockroaches also live in cracks and crevices.
Fix holes in walls and floors. Clean surfaces and seal gaps with inexpensive silicone caulk. Repair damaged door seals in refrigerators. Use Temperature Extremes. Heating to 115 o F for 45 minutes kills all life stages of the German cockroach.