Oh! Well, I don't see a problem with it. As long as you introduce some new genetics into the mix every so often, it should be okay. Because of inbreeding, you're at a higher risk for negative recessive traits to show up. But since you're feeding them off (I assume), it won't matter!
you really have to ask a roach or insect forum... but i highly doubt that genetic with negative recessive traits show up in insects... or else bees and other colony insects would be all deformed... roaches are the same as bees... it only takes one egg or pregnant mother to infest an area... so i wouldn't be worried about it... or else roach breeders or any type of insect breeder would have insects with tail kinks too...