I raise hatchling garden skinks and small geckoes on roaches, I don't even have to use first instars. I don't think you're likely to hatch anything much smaller than a garden skink and if you did I'm sure a first instar roach would be fine.
Hehe, I've left colonies for many months and found that most of them have lived! They are obviously starved and wouldn't be good to feed off in that state, but after a few weeks of good feeding and a moult or two they'd be fine, and certainly okay for breeders. That's one of the good things about roaches, you can leave them almost indefinately and they go into a state of almost suspended animation as long as it's cool and not too dry, unlike crickets which will die after about 30 seconds of neglect.
The only benefit I can see crickets having over roaches is that crickets tend to run around in the open while roaches are more prone to hiding. Roaches breed and grow so quickly that crickets breeding faster just isn't an issue at all; you can produce many kg's of roaches in a year with colonies housed in three or four small buckets, and with about 5 minutes of maintenance per week. Try doing the same with crickets - you'd need more space, much more time, and it would probably cost more in feed.
