I’m unaware of way to do this. Try to use a network share instead. See also:
You can use the following guides to setup a share on your PC / laptop, but don’t add it as a watched folder if you want to use it as backup location:
FAQ: How do I create a shared folder on Mac and add it as a watched folder in Roon?
FAQ: How do I create a shared folder on Windows and add it as a watched folder in Roon?