A forecarriage (8) of a rolling motor vehicle (4), comprising a forecarriage frame (16), a pair of front wheels kinematically connected to each other and to the forecarriage frame (16) by means of a first kinematic mechanism (20), each wheel being connected to said first kinematic mechanism (20) by means of a respective axle journal (60), a roll block system (100) comprising a second kinematic mechanism (110) that directly connects the two wheels to one another at the respective axle journals (60) between two connection points and can assume a free configuration in which the second kinematic mechanism (110) can passively follow the movements of the two wheels with respect to each other without interfering with them and a blocked configuration in which the second kinematic mechanism (110) can set the distance between said two points thus preventing rolling movements between the two wheels while allowing pitching and steering movements.