The runout of the roller is a crucial criterion for rolling processes of metals, plastics or other materials. An imbalance is even dangerous for rollers which have to rotate at high speeds. Therefore, the roundness of the roller must be measured before and also during the application. For all the following processes, a sensor measures the roller directly and establishes the ovality. The non-contact eddy current method is used for rollers made of polished metal. Capacitive or laser triangulation sensors are used for rollers made of other materials.