Well the inotify based file “announcement” is more relevant when using local (non-network) drives (i.e., RoonOnNAS with local NAS storage).
The Automatic Rescan Interval is only available when using networked storage volumes. And while @James_H is indeed using networked storage, Roon doesn’t know that right now because his configuration is pointing to the local mounted volume rather than the “raw” SMB mount.
If @James_H reconfigures his storage location to point to smb://{NAS address}/music instead, then he should see the Automatic Rescan Interval setting, I believe…
That said, he might not even need the Automatic Rescan Interval if he wishes to use the tips at A Roon on (Synology) NAS Primer to increase the inotify limits on the NAS.