A roller-mill for mixing and plasticizing materials, comprises two tempered, rotatable rollers which are operable at different circumferential speeds. The rolls are long and are provided with angular grooves which are inclinedly disposed relative to the axis of rotation of the rolls. The grooves on the two rolls extend in opposite directions to one another. The grooves producing biaxial shearing in the nip between the rolls because material is reliably fed into the nip. The grooves also produce a simultaneous, axial conveying of the material. Along the roll nip, various materials which are to be mixed can feed-in simultaneously or successively and, depending upon the intended purpose of the end product, the materials are removed from the device for further processing in either a partially plasticized state or in a fully homogenized state, as desired.