The authors have investigated the residence time distribution of grains in the rolling bed of a continuously operating granulator disc, containing cone-frustum and cylinder elements, with an inclined axle by feeding (impulse disturbance) defined amounts of marked (coloured) substances. They have defined functions between the virtual, the C-function based and the reduced average (mean) residence time, and different parameters, such as the mass flow of grains, the rotation speed of the disc at three different axial angles. Furthermore, they have investigated how the operating conditions might effect the calculated mixing coefficient at predefined average residence time and known maximum concentration of marked substances. Using the optimal parameters, intensive mixing conditions are produced in the rolling bed, in a similar way to the fluidised bed.