To add some metrics to my earlier post, I have 9,755 releases in my collection and Roon only identified 6,909 of them. That’s a roughly 71% match rate, which isn’t great IMO.
I think this is largely because Allmusic doesn’t have great coverage of a number of genres I listen to (italo disco, African funk/afrobeat/boogie, techno and house, etc). Still, information on nearly all of these releases are available on Discogs, so the metadata is out there.