I looked it up today for another topic regarding tag export.
If it’s data from allmusic, there’s indeed a limit imposed by R1/allmusic (“Core data” is allowed, nothing else):
https://roonlabs.com/termsandconditions.html:
“Permitted Use” shall mean the (1) display on Your Roon system by You of AMG Data that is returned to You by the Lasso Service on Your Roon system solely while You are using Your Roon system to play or search through Your personal media files that correspond to such AMG Data and (2) embedding by You of only the Core AMG Data Elements within the ID3 tags of music files […]. For clarity, such Permitted Use shall not result in the permanent storage of AMG Data on Your Roon system, personal computers or other storage devices and shall not result in AMG Data being embedded in metadata tags of media files except as expressly set forth in this Permitted Use (for example, no non-Core AMG Data Elements may be embedded in ID3 tags of music files of End Users).
“Core Data” shall mean the following elements from the AMG Data: Album Title, Performer Name, AMG Genre Description, Track Title, Composer, Performer.
I don’t know how Roon handles cases where it would in theory be allowed to transfer data of “non-Core” tags (when it came from other sources which do not impose the same limitations as allmusic) or when entered by the user in Roon directly. But to be honest if I’d be Roonlabs I wouldn’t really invest much into this. Why making it easy to leave?
While I don’t know what is agreed upon between Roon and R1, I think it’s safe to assume when the end user is not allowed to use anything else than “Core Data” the software shall not easily expose “non-Core Data” to the end-user. Of course it could be just a design oversight to not allow copy and past but here we’d have a reason.