A roller shade adapted to be installed in a non-rectangular structural opening comprising a roller tube, a shade material, a hem bar, and a pair of longitudinal side channels. The hem bar may be extendable and may comprise a pair of wheels at its opposite terminal ends. Each wheel is adapted to be retained by and travel within one of the longitudinal channels which are adapted to guide the hem bar assembly along the side jambs and control an extension of the extendable hem bar as the shade material is rolled on or unrolled from the roller tube and the distance between the side jambs changes. The roller shade may further comprise a pair of tension modules adapted to be attached to the hem bar proximate to one of the wheels to provide tension on the hem bar assembly.