Best option would be to create another shared folder to store your music in (it is not a requirement to have this on ssd).
Go to your QNAP Control Panel to the “Shared Folder” menu and create it (if it does not already exist):
Then you can connect from the windows explorer to that share and copy your music files there.
After the copy process is finished, you need to add this folder in your RoonServer storage settings.
Click in the storage settings “Add folder” -> “Browse” and select it. RoonServer’s filebrowser should list all available shared folders. Select the folder, where you copied your music files.
If this does not work, please let me know. Just add @crieke somewhere in your message.
PS: If your QNAP shared folders are not listed in the filebrowser, please make sure you are really connected to it (and that you don’t accidentally have RoonServer running on your computer).