In this case unfortunately it looks like we need to use the fresh database. System-level backups have been known to cause issues with Roon, as mentioned in our Backup documentation:
Using Other Backup Applications
Because the Roon database is frequently being updated in the background with new metadata, cover art, artist information, and more, backing up your “live” Roon database using external programs can result in corrupt backups.
We strongly recommend against using Time Machine, Crashplan, Backblaze, or other backup applications to backup your “live” Roon database.
If you would like to use any of these applications to back up Roon, set up a Scheduled Backup and tell your backup program to backup the RoonBackups folder.
There’s unfortunately not much else that we can do here, but happy to hear you have Roon up and running again in the fresh state. If you have any other issues, do feel free to reach out to us again, thanks!