AceRimmer
(Smoke me a kipper, I'll be back for breakfast!)
9
Unfortunately Roon is a lot more bandwidth intensive and demanding than the vast majority of other on the fly streaming apps or services including 4K video.
It is also possible that there is something blocking the artwork portion getting through the network.
There are a few threads on this very matter fairly recently.
Possibly not useful for a solution but there may be something of interest in this thread