It will be nice to allow favorite songs to be downloaded to mobile phone for offline listening
Tidal allows for this only in their app, Spotify likewise, maybe qobuz too. If you have music of your own then you can I guess manage this yourself. Roon is unlikely to make this an option - make no sense.
I can confirm that Qobuz does indeed allow this.
I think this is well-covered in the Roon mobile feature request, so I’m going to close this out. Thanks!