To answer my own question, yes, it can be done. The roots that I planted now have green growth on them.

Hmmm That doesn't seem possible. Perhaps there was a tiny section of stem attached .

No stem attached at all. The root came from the bottom of the pot, it was growing out the drainage hole. When I moved the pot it came up out of the ground, so I cut it off at the bottom of the pot. Placed it in a seed starting mix with the top of the root level with the top of the soil, put a ziplock baggie over it, held on by a rubber band, for humidity. And sat it in a south facing window. It now has about a inch of new growth on it. Sorry, I didn't take any pictures, wish I had.

Wow, that's so interesting! Was the root woody or fleshy? I'd love to try it out of curiosity sometime. Did you leave any section of the root exposed to light ?

It was just a root. Sorry I should have taken pictures for reference. The only thing that was exposed was the top of the root.

The two I grew from root pieces, are growing well, although not very tall, full green and healthy looking.

The roots on my biggest brugmansia stretch super far as it's been in the ground for about 12 years . It's never sent up shoots from any of those roots, only right near the base of the stem/trunk