Ways of creating Roughness map from scanned fabrics

[pinarer]

I have been watching tutorials and one of the option looks like taking information from Normal map, then plug into curvature and with histogram range you create roughness

but if you already have multi angle images, like 8  angle images.  how you can pull the specular information and create the roughness ?
I couldn't find any information online on that.

any idea?
Thanks