Roaches are notoriously tough to control, because they reproduce so quickly. One German roach (the smaller kind) can lay 40 eggs at a time!
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Remove the Roach Welcome Mat
Do not make it easy for roaches to enter your home. Seal exterior openings to keep large roaches from invading. Most roaches are found in dark, moist areas like basements, cupboards, under kitchen sinks, bathrooms, and in openings where pipes enter walls. Keeping the basement dry and plumbing in good repair can help as well.
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Creatures of Darkness
Roaches have evolved to survive when fewer of their natural predators can see them, so they are more likely to come out in the dark when humans are less likely to squash them. Interestingly enough, just turning on a light will not spook a roach. It is actually the vibrations, noise, and air currents that scare them back into hiding, not the light itself.
Where do roaches come from?
German roaches (the smaller kind) live indoors and can come in from neighboring homes, apartments, condos, garbage areas, or basements. They can also be brought in with foods or other packaging such as cardboard cartons or paper bags. American roaches (the larger kind) usually wander in from the outdoors, especially in the southern area of the United States. They can be found outdoors around the foundation, near patios, under mulch, or in the sewer systems.
More Lines of Defense
Persistence is key. If roaches keep coming back, do not let them win.