Nope, never once really heard people talk about using the roots for something........you can tell by the fact that we immediately guessed your question wrong.

I myself would not put dead/dying/old roots into new soil as I agree with Daddy that it is inviting pathogens and unwanted things into your soil. Dead roots acidify things btw as they go.

Composting sounds like a good one. Otherwise nada I can think of....sorry.