Why does Roon Radio favor streaming?

I wish it flowed to us! Unfortunately we get nothing, and it flows away from TIDAL/Qobuz too. We get nothing and TIDAL/Qobuz get your subscription fee no matter if you play or not. They pay a large part of that income to the labels and use the rest to pay their bills. Every time you stream, they pay bandwidth out of their share of your subscription fee. Playing streaming content costs everyone.

It doesn’t. We’d need to see your situation with logs to investigate the scenario more closely.

Yes. There is a lot more music outside your library than inside it. Roon Radio looks at all the music it can play, not just your library’s subset. Given the large scale difference in the amount of content, I’d characterize that as a bias.