Cockroach infestations begin in two ways: either someone brings home cockroaches (or a viable egg case) or they crawl in from a neighboring infested area. If a home has poor sanitation—overflowing trash, food left out, fry oil out in the open, crumbs, or a dirty stove—then cockroaches may be attracted from next door. But they don’t travel far and aren’t likely to wander if they have food, water, and shelter where they're at.