Abstract: A standing seam roof assembly having adjacent roof panels supported by underlying support structure in overlapping edge relationship to form a standing seam between adjacent roof panels, a first roof panel having a female sidelap portion forming male insertion cavities and a second roof panel having a male sidelap portion inserted into the male insertion cavities to form the standing seam assembly. The male sidelap portion has a tang member that lockingly engages a retaining groove of the female sidelap portion. The standing seam assembly prevents unfurling of the first and second roof panels by forming multiple force couples that resist forces due to uplift of the first and second panels. Mastic is placed between portions of the female and male sidelap portions to form a weathertight seal.