The Roughen section of the Substance Lab gives certain parts of your texture a rough appearance.
Properties
Property
Description
Grit Density
Controls the density of the grit used to make your material look rougher. Larger values result in a finer grit. This property will only make a different if at least one of the following two properties are set to a value greater than zero.
Grit Depth 1
Increases the roughness of areas of the texture that correspond to darker areas of the master noise.
Grit Depth 2
Increases the roughness of areas not covered by the previous property. For an even roughness throughout your texture, set both Grit Depth properties to the same value.