I was unable to figure out how to use a file share name and path to get Roon to back up to an external hard drive. Therefore, I used the suggested easier method of plugging a USB drive into the back of my Innuos Zen Mini Mark III, which I use as a ROCK. The backup worked well. Thank you, Suedkiez!
Glad to hear you were able to solve it. Thanks for confirming that the USB backup worked well, and we’ll go ahead and close this one out. Enjoy your music!