Abstract: The structure of the present invention simplifies a roofing procedure at the ridge of a roof, ensures easy detachment and relocation, and enables ventilation of the air via the ridge. Each roof plate 10 has a third projection board 43 and a second projection board 42 protruded from the upper face of a roof plate member 12. The roof plates 10 fixed to roof rafters N are covered with a ridge capping 120 at the ridge of the roof. The ridge capping 120 has skirt elements 123 and rear projection plates 125 protruded from its lower face to be fitted in the recess defined by each pair of joint members 14L of the adjoining roof plates 10.