Using an ORM map in Substance Painter

Hi and thank you in advance! I've been having such a difficult time finding a solution to this online, so hopefully someone here can help.

I'm trying to import ORM textures I made for an UE4 project back into substance painter for editing but I'm not sure how to extract the roughness and metallic values correctly. What I'm doing currently sort of works but I'm unsure whether it's actually correct.

The current workflow: The workflow is almost identical for metallic values so I'm only writing on how I do the roughness. I add a fill with a roughness of 0.5. I'm going with 0.5 for roughness because that's what UE4 defaults to. I now add another fill above it with only roughness, and on the roughness slot I put the ORM texture. I add a black mask and a "grayscale conversion" generator on the mask. I change the grayscale type to green channel, which is the color of roughness in the ORM map. I then put the ORM texture in the grayscale generator's image input. I leave everything else as is.

Without the first step, where I add a roughness fill with a value of 0.5 the roughness will have partly transparent parts which will default to a roughness of 0.3 and I'm unsure whether it does that in UE4