Like translating Ra 1.6 to the apropiate roughness value between 0 to 1? Because Roughness values are always displayed on technical drawings to specify how rough something should be. I think it could be usefull to make realistic materials, when using values like that instead of "quessing" based on the perspective of the creator/artist.
https://en.wikipedia.org/wiki/Surface_roughness#Amplitude_parameters
No, because Roughness in Blender is a visual trick to simulate surface roughness and (according to the mentioned article):
[...] surfaces which are obviously different to the human eye [...] Ra fails to distinguish between two surfaces where one is composed of peaks on an otherwise smooth surface and the other is composed of troughs of the same amplitude.
So: different looking surfaces can have the same Ra value.