It is not recommended to point the container path to your old folders as used by RoonOnNAS app. Are the backups recent ones? Then you can easily copy the whole content of the previous backup folder /Major-Stuff/RoonBackups into the new one living under /Container/roon-backups and roon should recognize it, once you are searching for a backup to get restored.
Regarding accessing the files of your music library, try as the second path in the container setup:
/share/Major-Stuff/Roon_music:/Music
This should work, if the top-level folder /Major-Stuff is correctly mounted on the volume Data-Vol1