This happens if you import files that have artist tags and these artists are not yet credited on an identified album that is already in your library.
The workaround is to first have such an album in the library. Easiest by using a streaming service.
You can also merge the duplicate artist into the real one after the fact - but for merging you still have to have an album with the real artist credit in your library, so you don’t win anything by doing it this way.
Later you can remove any unwanted albums from the library again.
A similar thing happens when editing album credits within Roon. Cause and workaround are the same.
I wrote about the second case here, and there are further links from this thread to other topics discussing other variations: