Cockroaches can sneak into your restaurant several ways. One of the most common ways cockroaches enter restaurants is on food related goods shipped to you from suppliers that may have infested warehouses or transport trucks. Cockroaches live in cracks and crevices. They are particularly fond of cardboard boxes and paper bags that provide both a harborage and food source.
Sometimes floor drains and plumbing lines can be a source of cockroach infestation where certain troublesome species like Oriental and American cockroaches can enter a building.
Loose window screens, holes in walls, cracks under doors these can all be entry ways into your restaurant for your most unwanted guests cockroaches.