I breed 4 species of roaches, and I'd agree with Ethan that the lateralis are the fastest reproducers and they make up the bulk of my feeders. They elicit a greater feeder response because of their activity level. The dubia nymphs are fine if your geckos will feed from a dish or tongs, but they tend to "freeze" in place and most geckos will pass right by them and not recognize them as food unless they move.
My adult dubias and discoids are just "nymph factories". I don't have anything large enough to eat them, and I certainly don't have the time to cut them up into bite sized pieces. If I had to "slice and dice" adult dubias to make them a feedable size, I think I'd go back to crickets.
And as for the blaberus hybrids... I don't keep any, but from what I understand, they do breed on, and may in fact be a bit more productive simply because of the genetic vigor the cross brings. A lot of people's feeder roach colonies are actually rather inbred and over a period of generations, and that can lead to reduced production. I try to add in some new roaches occasionally to refresh my lines, but I produce more than I can use anyway, so it's not a big concern for me. As far as I know, we don't have a lot of "wild blood" being added into the feeder roach population. Not because it would be difficult to do, but simply because it's not seen as a real priority. Crossing a couple of the blaberus lines probably does give a fresh infusion of blood that results in higher production.
Gary Hamann
Ridge and Valley Reptiles