Things may change in future
It turns out that exterminating cockroaches is actually quite easy, if you use modern science to help you out. The problem with most methods of killing cockroaches is that the cockroaches have tremendous selection pressure to evolve ways of not getting killed. The way around this is to use a method which they will find much more difficult to evolve out of.
That way is developmental disruption. A cockroach life cycle is a simple one; it hatches from an egg into a miniature cockroach, then goes through a series of instars, shedding its exoskeleton each time and inflating internal air sacs to make the soft new one a bit bigger than the old one. All the time this is happening, a gland in its head is pumping out a hormone called Juvenile Hormone, for which there is no equivalent in vertebrates. About halfway through the last juvenile instar the gland stops producing juvenile hormone, and the final exoskeleton that forms is a little different from all the previous ones; it has genitalia and other adult characteristics.
If you produce an artificial analogue of juvenile hormone and keep giving this to last instar cockroaches, then their adult exoskeleton looks just like a juvenile one; no genitalia. Such animals cannot breed, and do not undergo any further moults either; they live out their lives without breeding. Juvenile hormone analogues that are thousands of times more bio-active than the real one, and much more persistent have been developed.
This means that if you want to permanently keep the cockroach population in a building near to zero, all you do is periodically saturate the place with a juvenile hormone analogue. You'll always have a few cockroaches coming in from the surrounding area, but the offspring of these incomers never themselves breed.