The save location is the same USB connected HD that holds my music so obviously Roon can access the same to read at least. Do you have any idea on what is wrong here?
Apparently the Roon does not like the original drive. It is Mac formatet some years back (HFS+ I believe) but I was successful when mapping a Dropbox folder and later an ExFAT formated USB thumb drive.
With this I consider my support case closed and thank everyone contributing to reaching here.