Movie recorded in fluorescence mode of a dense suspension of microrollers driven by a rotating magnetic field. Only 1:1200 particles are fluorescently labelled and therefore visible here, enabling the tracking of the dynamics in the microrollers suspension. Particles with zero mobility (i.e. stuck to the wall) or overly bright particles (i.e. clusters) were left out of the analysis. The playback is in real time and the microscope images were blurred using a 1 pixel Gaussian blur to improve visibility.