Interfacial transport of a passive scalar from a gas to a thin liquid film is considered. The base flow in the liquid is laminar, with linear velocity profile produced by gas shear. The velocity disturbances imposed by waves are simulated by an inviscid, constant-vorticity model. Numerically computed roil waves are shown to enhance interfacial transport by modifying the convection pattern below the crest and by inducing a mixing effect on the substrate. It is argued that the entire wave spectrum is active in this enhancement of interfacial transport.