For the roughness: Create a design that has some variation in roughness. For a quickie, you could use one of the grunge maps that Substance Designer has built in. Hook that up to a Histogram Range node, and this allows you to control your roughness range and intensity. Plug that node into the output node for roughness. The…
I'm wondering why you're using an imported image for the roughness map? The Histogram Range node is pretty cool, where you can set the controls in the node, and then control the range in Substance Painter or Unreal Engine. I'd honestly just use that instead of a levels node. Also, the roughness range isn't going to be very…