with the charging stock 28 to be comminuted i e non precomminuted cement clinker having a grain size of for example up to 100 mm being supplied therewith via a charging shaft 29 the grain size of a substantial part of the charging stock 28 is greater than the width of the narrowest nip of for example 20 mm between the two pressing rollers that for example can have a diameter of 900 mm the pressing power of the rollers of the roller press pressing on the materials 28 and 20 amounts to more than 2 t per centimeter of roller length for example 6 through 9 t cm the charging stock is comminuted in the nip between the rollers due to a combined individual grain crushing and interparticle crushing for the implementation of this latter comminution principle the charging stock to be comminuted is supplied to the nip of the press 27 in such a great quantity by the charging shaft 29 arranged above the nip so that the material to be comminuted and drawn in between the rollers by friction presses the rollers apart and the particles of the charging stock crush one another in the nip in a fill a collective or in a product bed the cement clinker emerges from the nip comminuted and partially agglomerated i e pressed into scabs 30 whose proportion of particles already reduced to the desired cement.