Roaches can hide in many places around the perimeter of your home and in your home itself.
Seal off cracks and crevices with a caulking gun.
Seal off holes surrounding pipes or other light and wall fixtures with a material such as copper mesh.
Make sure window and door frames are tight and gap-free, to prevent entry from outside.
In areas that have heavy roach traffic, place tape over holes and crevices in appliance and other household items.
Computers and small appliances can serve as harborage for roaches.