Similar posts mentioning Rekordbox seem to complicate the issue with requests for more DJ features.
I’ll keep this simple:
Roon should be compatible with Rekordbox.
Rekordbox would connect to the Roon library, local files only, as it does “iTunes” music library.
Playlists created in Roon, should be visible/accessible in Rekordbox.
One-way is fine Roon–> Rekordbox; no need to pull anything back into Roon.