I picked up on Plex from the Roon forum as Plex adding Tidal has been creating some chatter amongst Roon users. I've not got the lifetime membership yet, still on the annual one but will probably go down the lifetime route if nothing else emerges soon.
I'm not sure you need to upgrade your endpoints to get the most from Roon, depends what you want from the multiroom setup though. I tend to have a critical listening place and then the multi room stuff is less hi-fi. I should try Plex to see what the features are like but a quick rundown it looks like there's a fair bit of metadata missing that Roon has.
Most Roon users seem to want an alternative to Tidal so Qobuz would be interesting. In short I've stuck with Roon because I really enjoy listening to music with it. I do find it difficult to spend that sort of money on software though.