It would be helpful if Roon picked up image files and PDFs that were stored in sub-folders named “covers”. So far as I can tell, this function is limited to sub-folders named “art”, “artwork”, and “scans”, but there may be others.
Ideally, it would be great if image files were indexed for an album irrespective of the sub-folder name but I don’t know if there are any restraints preventing this…