Abstract: Multicolor flexographic machine comprising a plurality of printing units, a robot in close relationship with the printing units and arranged to remove in succession each block-holding roller from its working position on the flexographic machine, to place it on a roller support trolley and to replace it with another block-holding roller available on the roller support trolley. A system for presetting the block-holding rollers is provided to obtain correct printing overlap in the machine and is controlled by an actuation unit which governs a contact-separation sequence of the rollers in each printing unit with micrometric adjustment of the roller pressure. Each block-holding roller is held in position free to rotate by automatically opening and closing holding caps.