D.E. / Diatomite can kill any bug with an exoskeleton ... and, that includes ALL cockroaches. This video shows a cockroach in a jar with no escape from D.E., & it walking & moving in the D.E. It nicks & cuts its exoskeleton, allowing the dry & very absorbent D.E. to absorb its body moisture, until it dies.... If given a choice, the ants I treat with D.E. touch it once & turn away ... even from a plate of cat-food. (I put a mote of it in a dish under the food-bowl). Instructions for using D.E. include ... putting it where the insects come in from outside, to turn them away before they ever get inside! Https://www.youtube.com/watch?v=lAKQO7duPHU
Although diatomaceous earth does not work while wet, it will work once again once it dries. Our use is to keep roaches out as I live in the south. I mix it with water and spray it all around my kitchen. Once a dries it works again and I have no roaches. Also use it on my pets. I have seven dogs.
@Angie, I know it has been awhile since your post but I wanted to throw in my two cents and say that in my experience the size of the bug is not important. A few years ago I lived in an old apartment surrounded by lots of foliage, and the space underneath the front door was literally at least an inch and a half (letting in all sorts of bugs! ) I literally dusted a thin line of DE across the carpet there, and after that, the only time I saw bugs inside, they were dead. Which yes, was pretty gross, but better than having them crawl around. Good luck.