Hi @opmetuan,
The current implementation will prioritize the highest resolution image named (or containing) the substrings folder, cover, or front. But as @BlackJack mentioned, Roon will technically scan all PDFs that are exposed within a Watched Folder.
Some users have long felt this cover art priority overlooks their curation style. Here’s a an old feature request that actually still generates considerable internal discussion on the Product team. If you feel strongly, please create a new #featurerequest here.
The best workaround for now would sadly be the laborious one - remove the unpreferred, higher resolution file from the artwork or album folder where Roon is finding it, leaving only the cover.jpg file.
Hopefully this helps!