Welcome to the forum and thanks for the details about the ROCK installer hanging during handover on the NUC10i5FNH.
What exactly do you mean by handover? Have you enabled UEFI mode, and did you disable Secure Boot? Have you followed the ROCK installation guide? Can you try the other flash utility mentioned in the guide?
Not sure about .BIOS file. I downloaded FNCML357.0067.CAP put it on a thumb drive & installed it on NUC. Updated that to latest version on NUC. PRoblem is after that I tried to install a new usb thumb drive with the Roon Rock (roonbox-linuxx64…img) I scroll down to the thumb drive, press enter then screen goes black and nothing happens. Tried with different thumb drives.
Two things worth checking, and the BIOS one is likely: flashing 0067 reset every setting back to defaults.
BIOS. Please power on, press F2, then F9 to load defaults, and set:
Secure Boot: disabled. ROCK will not boot with it on.
UEFI boot: enabled, legacy boot disabled.
Boot order: USB first.
F10 to save. Full list of settings:
The USB drive. The download is roonbox-linuxx64-nuc4-usb-factoryreset.img.gz, and it has to be flashed with a tool like Etcher, not copied onto the drive. If the file was decompressed and copied across as a file, the drive still shows up in the F10 menu and then does nothing when you select it, which matches what you are seeing on every stick you have tried. Could you let us know which tool you used to write it?