A roof bar assembly comprising: - a pair of support rails (3a, 3b), namely a first support rail and a second support rail, intended to be fastened on each side of a vehicle roof, each support rail (3a, 3b) being parallel to a longitudinal axis (XX') defined by the vehicle, said support rails (3a, 3b) being aligned in a substantially horizontal plane, - at least one bar, having a central segment and a pair of end segments (4, 6), namely a first end segment and a second end segment, wherein the first end segment is pivotally connected to the first support rail so as to allow the positioning of the bar according to two specific use positions, respectively a longitudinal position, in which the central segment is substantially parallel to said longitudinal axis (XX'), and a transverse position, in which the central segment is oriented substantially perpendicular to said longitudinal axis (XX'), and wherein the second end segment is adapted to be fastened in a manually removable manner on the first support rail, when the bar is in its longitudinal position, and on the second support rail, when the bar is in its transverse position, characterized in that the first end segment and the second end segment are pivotally connected to the opposite ends of said central segment, and in that the length of the bar in its longitudinal position is larger than the distance separating the support rails (3a, 3b) such that the distance separating the central segment from the plane defined by the support rails (3a, 3b) is greater when the bar is in its transverse position than when the bar is in its longitudinal position. - a pair of support rails (3a, 3b), namely a first support rail and a second support rail, intended to be fastened on each side of a vehicle roof, each support rail (3a, 3b) being parallel to a longitudinal axis (XX') defined by the vehicle, said support rails (3a, 3b) being aligned in a substantially horizontal plane, - at least one bar, having a central segment and a pair of end segments (4, 6), namely a first end segment and a second end segment, wherein the first end segment is pivotally connected to the first support rail so as to allow the positioning of the bar according to two specific use positions, respectively a longitudinal position, in which the central segment is substantially parallel to said longitudinal axis (XX'), and a transverse position, in which the central segment is oriented substantially perpendicular to said longitudinal axis (XX'), and wherein the second end segment is adapted to be fastened in a manually removable manner on the first support rail, when the bar is in its longitudinal position, and on the second support rail, when the bar is in its transverse position, characterized in that the first end segment and the second end segment are pivotally connected to the opposite ends of said central segment, and in that the length of the bar in its longitudinal position is larger than the distance separating the support rails (3a, 3b) such that the distance separating the central segment from the plane defined by the support rails (3a, 3b) is greater when the bar is in its transverse position than when the bar is in its longitudinal position. wherein the first end segment is pivotally connected to the first support rail so as to allow the positioning of the bar according to two specific use positions, respectively a longitudinal position, in which the central segment is substantially parallel to said longitudinal axis (XX'), and a transverse position, in which the central segment is oriented substantially perpendicular to said longitudinal axis (XX'), and wherein the second end segment is adapted to be fastened in a manually removable manner on the first support rail, when the bar is in its longitudinal position, and on the second support rail, when the bar is in its transverse position, characterized in that the first end segment and the second end segment are pivotally connected to the opposite ends of said central segment, and in that the length of the bar in its longitudinal position is larger than the distance separating the support rails (3a, 3b) such that the distance separating the central segment from the plane defined by the support rails (3a, 3b) is greater when the bar is in its transverse position than when the bar is in its longitudinal position.