Load support structure for use on roof

A roof load support structure supports a load on a sloping metal panel roof such that substantially all of the load is conveyed through rails, which are mounted on roof panel ribs, thence through the roof panel ribs, and to underlying building support structure. Minor portions of the load can be conveyed through an upper diverter and a lower closure. The upper diverter diverts water laterally away from the support structure, in two opposing directions to two opposing sides of the support structure. The support structure spans at least first and second ones of the roof panels. Cut, terminal ends of an intermediate rib are cantilevered from purlins immediately above and below the support structure, and thus support middle portions of the upper diverter and the lower closure.