If you have such sites, try to keep them dry. If you must water, periodic treatments of such sites will reduce the nesting and reproduction of roaches. Other preventative measures include sealing windows, pipes, cables and siding with caulking. Damaged siding should be repaired. Cracks in concrete walkways should be filled.
Roaches are opportunistic.
They will take advantage of any site, which provides moisture and protection. The second way of dealing with these roaches is to treat their nest sites. Instead of waiting till they move inside, treat outside areas such as mulched shrubbery beds. I recommend Maxforce Granules for these areas. The granules will sink down to where it counts.