For those that have TrueNAS running this would be optimal. Especially given ambient resources that would be available for consumption by Roon.
Best way to run Roon on a NAS is in a VM. Then you are isolated from NAS OS update issues (cf. DSM6->DSM7). Let the VM house the Roon database, and use a mount back to TrueNAS to target Roon backups to. If you have local music, you can also use a (ideally read-only) mount back to TrueNAS for that as well.