A roller mill includes a rotatable grinding table, at least one grinding roller that is retained rotatably on a pivot lever and is in rolling engagement with the grinding table, with the pivot lever being arranged for pivoting about a pivot lever axis, and a drive train associated with the grinding roller in order to drive the grinding roller with a fixed motor. The tissue suturing instruments are designed and configured for suturing tissue grasped thereby to soft tissue as well as to hard tissue. Operations of the frequency conversion circuit and the signal processing circuit are controlled by a control signal outputted from a control circuit arranged outside the metallic case.