Then I suggest you contact QNAP support like the OP from the thread linked above did so they can (maybe) help you find out what software changes your file or file attributes.
Note: It’s not Roon that changes the file (attributes) on your NAS as far as I’m aware.
This possibly is the solution, at least for the OP from the other thread, as it seems its Mac computer was responsible for the unwanted changes to the file on the share. Maybe you can find another way to prevent your computer from accessing and changing files from your Roon Server installation on the NAS? Maybe something simple as marking the file as read-only?
Note: There is no need for the Roon Server installation to be on a share (accessible from other computers) I can think of.