You've probably ended up on this page after seeing an error message similar to the one below:
This article provides more details regarding this limitation. This limitation only applies to zones that:
There's some extra technical complexity when performing grouped playback to zones with custom MUSE configurations. Combining these features requires Roon to send a different audio stream to each zone, and in some cases requires us to synchronize playback between streams playing at different sampling rates.
In some cases, the relevant playback technologies simply don't support these concepts and could not be made. In other cases, they are theoretically possible, but the effort that would be required hasn't been justifiable.
Roon supports these use cases fully for situations involving
RAAT, as it was designed from the start with considerations like this in mind. It's possible that we'll be able to deliver this functionality to some of the other technologies in the future, but this is not currently on our roadmap.