Roon uses a reverse-engineered solution for Airplay[1], which will resample the source, and is why you see the green, high-quality, badge. In contrast, native Roon Sonos support directly sends a bit-perfect signal to the Sonos endpoint.
Airplay2 streaming is only available on Apple devices, so I would guess that Sonos has to support both AirPlay[1] and Airplay2 on their devices, which is why @Bert is using an Airplay2 device with Roon. But I suspect the signal path will only show high-quality, as with Airplay[1].