NAS Storage question

I have a QNAP NAS which is where all my music is stored approximately 3TB worth
I have downloaded all that content to ROON on my Windows 10 PC, if I shut the QNAP NAS down will the content on ROON that I put into be gone and have to be reloaded when I start up the NAS again, I’m just not a big fan of leaving electronics on if I don’t have to or do I need to keep it on to avoid all the reloading?

Yes, Roon doesn’t touch or ‘download’ your local files. It just reads the files at the locations you have specified in Settings==>Storage.

A NAS doesn’t really work if one shuts it off when not in use.

Do you shut off the Roon Core machine when not using Roon? If your answer is yes, then attach a USB external drive to the Core machine and don’t use a NAS at all for Roon.