The invention relates to a roller mill, particularly an air-swept roller mill provided with a device for separating magnetizable constituents, particularly iron particles from the milling area. The invention also relates to a method for grinding materials with magnetizable, particularly iron-containing constituents, e.g. slag, in an air-swept roller mill where, for avoiding concentrations of magnetizable particles, particularly iron particles, on the grinding pan, said particles are electromagnetically separated and removed from the roller mill.