I have the same issue described here last night: Qobuz is not working with Nucleus+
While there can be regressions, the reason for spending $$$ and getting Nucleus+ with Roon is hoping better support when things go wrong. I see no way to reach support apart from posting here and hoping and praying somebody from Support see it :-(.
If you find a solution, please post, I will do the same. I only subscribe to Qobuz and with it not working, I am completely cutoff from streaming via Roon!!
thx
Sridhar