A roof assembly for a vehicle roof opening comprises a pair of guide rails extending in a non-parallel way and at a distance from each other. At least one closure element is adjustable in order to at least cover and at least partly open the opening. At least one pair of sliding elements opposite of each other on each of opposite sides of the closure element is provided for slidably engaging in the respective guide rail. The sliding elements are slidably connected to the closure element in a substantially lateral direction. A biasing device is used for biasing the sliding elements relative to the closure element in a substantially lateral direction by being attached to the closure element on one end and being operatively connected to each pair of opposite sliding elements on the other end with interposition of a synchronizing device equalizing the movements of the sliding elements.