Will all data be deleted?

If I delete an album from my NAS, will all Roon data for that album (pictures, text, metadata) also be deleted from the Roon folders?
Also, if I replace a picture chosen by Roon with one I like more, will the old picture be deleted from the folders?
I don’t want to end up having a lot of unwanted data lying around on my NAS.

Yes, after you have run : Roon --> Settings --> Library -> Cleanup

Roon always retains and maintains the “default” data is pulls down from the cloud for an album, library edits including image changes are held in a different layer in the the Roon metadata model.

That said, compared to the music files themselves the amount of storage occupied is trivial in comparison.