Does Lumin allow Spotify Connect on your D1? It seems like Spotify is a lot like Apple with their consumers - they want their consumers to stay within their ecosystem, which limits or denies access to their content from other platforms/businesses. For example, If you have BluOS (Node) and select Spotify, it will automatically kick you back to Spotify’s app with implied encouragement to use Spotify Connect so you can stay within Spotify.
Unsure if there are any other third-party platforms that could mimic Roon’s UI and functionality, while using your Lumin. If Spotify delivers with their Hi-Fi content and you have a streamer (which I believe you do) that allows for Spotify Connect, you may not need Roon (Spotify’s UI is pretty good, music discovery) or Tidal (Spotify has a deep library).
Personally I like Roon A LOT and think Spotify pushes too many podcast on their user landing page. But at the same time, I could also see myself transferring playlist from both Roon and Tidal over to Spotify once Hi-Fi is released.