Displacement is the LightWorks shader where you put your channel mask if it is not already in the iimage file.
This is complex because LightWorks actually bridges between the way the internal engine sees a texture and the way LightWorks does.
If the image has an alpha channel, then Lightworks uses it for specified shader effects. If not, it looks for an image file in a shader parameter list.
Mostly we uses "rough" to make surfaces have less glare, approximating paint applied by a roller..... or stucco or whatever.
See attached.
Dwight Atkinson