Abstract: A roof structure for a building includes a number of panels, preferably of a sandwich construction with a rigid foam core and upper and lower surfaces which may be metal, wood or other material depending upon the use. A first type of joint extends along the fall line of the roof, with the panels being in side-by-side, spaced relation and supported along their ridges by a roof truss extending along this longitudinal joint. A retainer strip extends along the longitudinal joint and is held in sealing relation with the adjacent panels by means of threaded fasteners secured to the truss. A joint transverse of the fall line is formed by a tongue-in-groove construction of the panels which permits an upper panel to lap over a lower panel for better drainage, and also allows for thermal expansion and contraction.