I have given my Salamandra salamandra and Ambystoma spp Nauphoeta cinerea. I have read that they are suposed to have softer shell than other roaches and therefor are better as food since other roaches have to hard shell for caudates. It seems to have worked out fine since i had no problems so far.
I dont know if roaches in generall have to hard shells for caudates to ingest since diffrent reptiles of varios size doesnt have any problem. And i have found no source that says that amfibians have less effective digestionsystem than reptiles (for example leopardgeckos)
I know that for example toads of diffrent kinds (bufo alvaris and other) can have problem with larger kinds of roaches. Sometimes the shell comes out undigested. That my cause impactation in smaller caudates perhaps? The toads dosent seem to suffer from it though.
Nauphoeta cinerea has the nasty abillity ty climb on glass though so feding may be a hassle. But nothing is easy... Spelling in english can be qute hard for example. Hope you understand at least something i write... sorry