I do not have Poser 12. Anyway, the change in the Blender Cycle nodes regarding roughness is exactly as I wrote. In older Cycles the value was assumed to be linear, but that was not compatible with the PBR roughness maps. For compatibility reasons, all older Blender Cycle node setups used a mathematical node that calculates the square value from the roughness before feeding it into the (old) Cycle nodes to be compatible with the PBR roughness maps... very simple.