So the manual says:

Metallic - replaces the slot of Specular Channel
Roughness - replaces the slot of Reflection

Test result of conversion:

Roughness takes inverted Specular Channel (which is fine I can re-invert it and adjust as I wish)
Metallic takes nothing - just black

Why?
I can sure drop the maps manually after conversion, but it would be nice to have an automated conversion consistent with the manual.

On a positive note - Color Adjustment panel is great!