The lifetimes of molecules located close to a sinusoidal grating surface are studied within a classical phenomenological model. The contribution of surface roughness to the molecular decay rate is attributed to the discrepancy between the experiments of Rossetti and Brus and the theory of Chance, Prock, and Silbey. It is found that surface roughness can either enhance or diminish the flat-surface value for the decay rate depending on the emitting frequency, molecule-surface distance, and the molecular orientation.