A vehicle roof opening having a cover and bearing device which displaceably supports the cover on a roof-side longitudinal guide rail a front and rear bearing unit, which moves the cover between a closed and at least one deployed ventilation positions. The front bearing unit may have a bearing arm, one end which pivotally mounts the cover and the other end which is slidingly and pivotally mounted on the longitudinal guide rail; carries out a positioning movement controlling the cover front region, when said cover is moved from its closed position into its ventilation position and/or into an open position. The bearing arm may be pivotally mounted by a rocker-type bearing having a pivot bearing and two sliding elements, on the longitudinal guide rail in a slidingly mounted bearing carriage, and a pivot-control unit guides the two sliding elements to achieve the rocker-type pivoting action of the bearing arm.