It is a good thought … and … no I have not … because that is very much harder work, particularly since using Roon my file labelling has been much more lax, and combined with this, I am often trying to delete the non-preferred version. BUT! You are right, I should try it just as an exercise to gather information though, maybe, nothing else.
It means that Roon was accesing your files at the time you were trying to delete them. That shouldn’t be happening all of the time so, yes, it does sound like something odd is going on!
This means that another process has a lock on those files, so Roon cannot delete them. Do you have an antivirus scanner or backup running from time-to-time?
I have learnt some things. Resource monitor! In ‘Associated Handles’ a search for Roon reveals only a couple of Microsoft registry files, but they are being accessed by Roon itself. Mmm?