A roof panel includes a planar body having top and bottom edges, with a downturn edge extending therebetween, and an opposing channel edge. The downturn edge overlays a channel edge of an adjacent panel. The bottom edge overlays a top edge of another adjacent panel. A plurality of courses extends between the channel and downturn edges. Each course includes a nesting ridge to receive the downturn edge of an adjacent panel and to position a top surface of the panel flush with adjacent panels. Surface channels and contoured ridges are defined within each course. A drain aperture of the drip edge aligns with an adjacent channel edge to direct material through the drain aperture and onto adjacent panels. A gable member engages an edge when the panel has one or fewer laterally adjacent panels, wherein the gable member is flush with the adjacent planar body.