A roof device for an opening roof, comprising: - a plurality of stackable panels which are configured so as to be movable along a rail system, wherein the movable panels are configured such that they can move repeatably between - a first, closed roof state in which the panels lie aligned next to each other in the same plane; and - a second, open roof state in which the panels lie aligned and stacked one above the other, and wherein the movable panels comprise: - a rear panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the second, open roof state; - a front panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the first, closed roof state, characterized in that said roof device further comprises - a connection system configured for repeatably coupling adjacent movable panels which lie next to each other in the closed state, by a downward movement of the rear panel wall of a top movable panel along the front panel wall of a bottom movable panel in the open roof state, wherein the connection system comprises connection elements and connection points for the adjacent movable panels, arranged such that the connection element of each movable panel is configured for repeatably coupling with a connection point of an adjacent movable panel; and wherein the connection element comprises a downwardly pointing body which extends laterally from the rear panel wall; and wherein the connection point comprises an upwardly pointing body which extends laterally from the front panel wall, wherein the connection system furthermore comprises at least one stiffening element comprising an upwardly pointing body which extends laterally from a said movable panel. - a plurality of stackable panels which are configured so as to be movable along a rail system, wherein the movable panels are configured such that they can move repeatably between - a first, closed roof state in which the panels lie aligned next to each other in the same plane; and - a second, open roof state in which the panels lie aligned and stacked one above the other, and wherein the movable panels comprise: - a rear panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the second, open roof state; - a front panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the first, closed roof state, characterized in that said roof device further comprises - a first, closed roof state in which the panels lie aligned next to each other in the same plane; and - a second, open roof state in which the panels lie aligned and stacked one above the other, and wherein the movable panels comprise: - a rear panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the second, open roof state; - a front panel wall, which is a side wall of the movable panel oriented in a direction of movement of the movable panels to the first, closed roof state, characterized in that said roof device further comprises - a connection system configured for repeatably coupling adjacent movable panels which lie next to each other in the closed state, by a downward movement of the rear panel wall of a top movable panel along the front panel wall of a bottom movable panel in the open roof state, wherein the connection system comprises connection elements and connection points for the adjacent movable panels, arranged such that the connection element of each movable panel is configured for repeatably coupling with a connection point of an adjacent movable panel; and wherein the connection element comprises a downwardly pointing body which extends laterally from the rear panel wall; and wherein the connection point comprises an upwardly pointing body which extends laterally from the front panel wall,