You should know that when you create the bootable usb with balenaEtcher, the file:
https://download.roonlabs.net/builds/roonbox-linuxx64-nuc4-usb-factoryreset.img.gz
becomes an EFI partition on the usb (hidden/system). If you want to re-use the usb stick or re-flash it, you first need to delete that partition, something that must be done carefully (see this post)