Very interesting insights and discussion ! Thank you very much @Brian and @danny.
I was also interested by What’s Wrong With UPnP
Would be very usefull to write a synthetic short paper with simple diagrams (for the dummies like me 
) to explain Roon / RAAT architecture and protocol, differences with others solutions (mainly UPnP / Airplay and perhaps LMS) and how these technicals points conducts to a better global user experience.