In addition to your recommended substrate, which works great, I have had success adding a fist full of dampened Sphagnum Moss to the roach bin. It's humidity seems to promote the ejection of healthy hydrated egg cases, many inside the moss. It is my understanding the Sphagnum Moss is antibacterial. I have not seen it mold, unlike some of the green mosses. The wide separation of tufted soft "leaves" makes moisture easy to get to for the newly hatched.