In the present research work, the role of surface roughness in the interlayer boundary formation during manufacturing of clad metal composites was analyzed. Process of interlayer boundary formation was described through mathematical and computer simulation. The importance of taking into account not only arithmetical mean roughness Ra or ten-point mean roughness Rz, but also Rz/S ratio (where S – mean spacing of adjacent peaks) is shown, because this relation affects the length of actual contact between dissimilar materials. As the result of mathematical and computer simulation, dependence of the length of actual contact between dissimilar materials on Rz/S ratio and semi-angle of the ridge vertex was obtained.