Hi @Marc_Mennigmann . Welcome to the community!
I don’t think the problems the Roon Not Showing Apple Music thread have anything to do with music downloaded from Apple Music. As long as the music is in the right format and not copy protected, a lot of people integrate their iTunes libraries into Roon.
But you’re right, Apple Music the service does not integrate with Roon. It takes both parties (Roon and the service provider) to agree to make accommodations for the service to be integrated. Tidal was first, Qobuz took a while to convince, and it doesn’t seem likely the big players like Apple or Amazon have much of an interest for integration, even if Roon would love to have them.