If you see them in light, there are usually many somewhere close by. The cockroach develops from an egg to the nymph stage, them to adulthood. From egg to adult takes about 3 to 4 months, and the adults may live for up to 1 year. The young work their way out of the packet in a few hours. The female lays 4 to 8 packets in her lifetime.
Cockroaches arrive in a house or dwelling usually by hitching a ride.
The carrier will most likely be a cardboard box which was stored in warehouse infested with cockroaches or any other carton or container which could contain the egg packet of the female cockroach. Therefore, be wary about bringing boxes into your home which may come from cockroach-infested places. Unpack such boxes in a garage where egg packets or cockroaches can be seen and killed with an insecticide. Use insecticides inside the house only when all other measures fail. If cockroaches do invade your dwelling, take steps immediately.