I found more!
We brought back a total of 5 skulls, 3 with lower jaws, but 4 of them had damaged enough sinuses that the roaches didn't seem to like em any. There were, in fact, 5 more! The skulls are now outside where the sun will scare out any remainder. I don't think there are any, though- I held the skulls perpendicular to the sinus cavities and smacked them until roaches fell out.
I got 4 at about 7mm, one at about 15mm. The first one I found has vanished into my peppered roach enclosure, but now that I have more, I've isolated these 5 in their own enclosure. For now they have an inch of coco fiber, a few hardwood leaves, and a bit of pretzel to chew on- I'm tired, so they get something makeshift. Later I'll put them in something with a topsoil/aquarium sand substrate, I think.
They came from a skull that was found under some sort of mesquite-type bush. A couple hundred yards from the water, I think. There were a lot of dead bits from the trees on the ground, and the ground itself was very sandy. It was definitely out of where the waves would even remotely get to, and sheltered from storms. It definitely gets pretty hot out there. Hopefully these are okay in less hot temps, I'm not gonna put them in something big enough to safely heat.
It was on the island Ni'ihau, which is a small island inhabited by about 200 people, off the coast of the rest. It's largely untouched by human activity, and I'm not sure how much it's been explored. I know someone introduced wild boars at some point, and eland antelope, and who knows what else, so these could be from Africa along with those? Could also be Hawaiian. It's almost in sight of the main islands in Hawai'i, so I think a flying roach could get blown out there in a storm, or it could have come out somehow on a boat.
I know I can't get a proper ID until they mature, but does anyone have any guesses at what they are? I don't know how to keep these!