Females of most cockroach species lay hardened, purse-shaped egg cases, called ootheca (ooth-EEK-uh), containing from 12 to 25 eggs, in dark, humid crevices.
Source: WelcomeWildlife.com

That would be them yes How do you keep your dubias?

On substrate 10cm, with the bark you see in the pictures.
they like to berry them self under the substrate.

And just give them food every 3 days and spray once a week with water.

I have about 200 in a plastic cargo trunk. no substrate, a bunch of egg cartons and live off salad off cuts (every 2 days odd), moslty spanspek peels. They love the stuff, but haven't had babies yet.

Oh crap.... I removed a lot of them ooths from my Hisser's home...

Thought it was some other insect that invaded their privacy...

Booooo-hooooo!

No worries there. The if you find ooths with your hissers they are abortions. Hissers females keep the ooths internally and until they hatch. Looks like she is pooping out little squirming white turds I have only 20 adult hisser but they have produced about 200 babies. I can't feed them off fast enough!