A physical model is presented for predicting the various roll-waves characteristics in inclined thin films and in the presence of various distributions of interfacial shear and external pressure drop. The model is based on a periodical distortion of the hydrodynamic boundary layer in the wave front, followed by a recovery process in the wave trail. The solution is a closed form at the inception or at the well-developed regions, where the frequency is also predicted. For the developing region, one input (frequency) is required. A satisfactory agreement between predicted wave characteristics and experimental data is obtained, particularly at the low-intermediate interfacial shear range. With increasing the interfacial shear, both the wave frequency and wave velocity increase, while the wave amplitude decreases, independently with the mode of interfacial shear distribution. Applying the present model for various prescribed shear distributions, while comparing with available data of measurable wave characteristics, stimulates some thoughts on the unresolved gas-liquid interactions.