Roon server installed on a machine with Ubuntu 17 release doesn’t see network folders (at least on my network) so keep it in mind if you have your music files stored on a NAS or on a remote computer.
Hope this helps
This should be working. Any chance you are missing the mount.cifs command? This usually comes from the cifs-utils package on Ubuntu.
Was it working on. a previous version of Ubuntu for you?
What have you tried so far?