Leveldb, which is the database that Roon relies on, is an in-memory system with disk flushes for persistence. But the databae on the disk is only guaranteed to be in a consistent state after a sit down. So Time Machine or any backup approach of the database is only going to work when the backup happens. And given how passive & unpredictable Time Machine is (feature, not bug) that means if you are relying on a TM backup of a Roon system that is always running, you’ll very likely be disappointed.
That said, Roon backups that happen through the Roon system write out only when the the core is effectively shut down/inactive. So once Roon has done a backup you can copy it however you want - rsync, active backup by Synology, drag and drop, Time Machine, whatever. They are just files. So long as you get the whole directory structure, you should be fine to back up the backup. The only risk is if you run your backup process while the Roon backup is active. But if Time Machine is rubbing reasonably frequently you’ll get a successful restore point at some point because a Roon backup doesn’t take that long.
Hope that’s helpful.