Unable to link Roon server on QNAP to Melco music files (ref#43RPS2)

Then additionally the Docker instance might lack the right to mount (remote) filesystems. Please note that there is no official support for running Roon Server in Docker. You can use the thread below to help you with that. The information regarding Docker applies to other systems running Docker too:

You can post related questions in that thread or create your own in Roon Software Discussion > QNAP/Synology NAS.

Alternatively: Install and use the officially supported Roon Server package.