OH my, you two certainly seem to have been burning the midnight oil on this thread! And to have the topic be how to grow more and healthier roaches, only herp people can read this and not be skeeved!
Since Elizabeth has more than adequately covered everything, I can only weigh in and support what she's already said. I particularly want to comment on the heat rock though. I would have concerns about trying to use it in my setup, but each of us knows more about our own situations than anyone else. If you think you can integrate it into your roach colony and solve the heat problem, without cooking roach eggs, then go for it. If it doesn't work you can always undo it later.
The other thing she mentioned is feeding roaches on adult bearded dragon food. This is what I use, and since I've been doing that, the health and vigor of the leo's eating the roaches (and also crickets, I use this in my holding tank for them as well) has been noteworthy. I can't stress this enough! I think if there is any one thing I've ever done to most improve the health of my gecko's, this is it!
Good luck, please let us know what you end up doing and how it works for you!
Todd