How to export MetaHuman roughness ?

Development Asset Creation
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1

Hello,
I know Unreal generates MH roughness map from Normals, but how do I export it using the “AssetsActions|Export” feature?

The texture exported is nowhere near the one you can see in the Texture Editor.

There’s a mention about the generation method on Epics’ documentation:

(ctrl + F: Roughness)

Thanks for your help