Abstract: An improved roller press for the high pressure interparticle crushing of a pulverulent material and the method of operating including opposed parallel horizontal crushing rollers forming a high pressure crushing nip between them and forcing air from the material drawn into the nip, a product delivery stack above the nip and an offset lower wall portion above the nip and laterally of the stack forming an exposed sloping surface of the material for the escape of air being pressed out of the material passing into the nip, in one form exposed surfaces are on both sides of the nip and the exposed surfaces may be controlled by adjustable gates to vary the area and slope of the exposed surface, and a subatmospheric pressure may be applied to the material for aiding in the pressing of air from the material drawn into the nip.