@Justin_Crosby if I understood it correctly, it is not possible to downgrade roon server on NAS to pre-2.65 version.
If you have an existing backup, it should be doable to copy the whole backup data into the /Roon-backup folder that has been shared with the container, and run a backup restore. You don´t need to create another backup.
If you don´t have any backup or it is very old, you can try installing roon server in the container, get it running, and subsequently replace the whole internal database in the container with a previous version from the RoonOnNAS folder. I have not tried this, but according to Roon staff member @vadim this should work:
Good luck!