I'm actually intrigued they have Green banana and Pallid Roached - the Pallids would be a fantastic choice as they are like mini versions of lobster roaches and very efficient breeders.The Green banana roach (Panchlora nivea) is also great and on the smaller side but is fast, and climb AND fly.

You could also try culturing Springtails - extremely easy to culture, virtually effortless and very tiny for the tiniest of frogs = )

Most species of prolific roach still take 2-4 months from birth to reach adulthood in optimal conditions and generally have a 1 month gestation time. Don't worry, give them some more time and they will begin to flourish. Once they reach adulthood, give them 3-4 weeks and you will have babies out your ears and will continually be producing them.