Roon subscribers presumably represent a tiny proportion of Spotify subscribers - therefore Spotify aren’t giving much up if they were to allow Roon integration. Presumably they can still monitor which tracks have been streamed so I can’t really see how they’d really be losing out on user tracking.
Similarly, the numbers are so small that Spotify won’t be worried about losing, potentially, every Roon customer to Tidal (unless Roon numbers swell to a large degree). I don’t see the value of giving up info on our owned collections and listening habits to Spotify as a bargaining chip - in fact, I’d be minded to think of it as a rather bad idea to share all that personal information.
I suppose all we can do is make out voices heard at Spotify and hope that they care enough to change their mind and allow Roon to implement their integration solution.
For me, Tidal is becoming more and more embedded in my listening life. A move back to Spotify is difficult without Roon integration as my lounge audio system is no longer ‘Spotify Connect’ enabled. I do miss some of my Spotify playlists, though.