A mechanical system forms a cam follower or a rocker arm. The mechanical system comprises: a support element, a pin extending between two opposite ends along a first axis and supported by the support element, and a roller adapted to receive the pin. The roller being mounted on pin, movable in rotation relative to the pin around the first axis and adapted to roll on a cam. The support element comprises two separate parts, generally semi-cylindrical, each having a contact face, in contact with one other, and a holding feature for maintaining parts assembled together.