Shock boundary layer interaction flow features are encountered in many high speed engineering devices such as turbine blades, air wings, intake systems for ram jet engines, etc. In the past, much works have been performed to investigate the shock boundary layer interaction characteristics and various interesting conclusions like boundary layer thickening, boundary layer separation and reattachment, shock unsteadiness, etc were derived. These findings are mainly obtained for flow over smooth surfaces. The local flow states induced by shock boundary layer interaction can strongly depend on the wall surface roughness but no detailed investigations were carried out in this regard. In the present study, numerical simulations were used to investigate the flow characteristics produced by the interaction of shock wave on boundary layer over a rough wall. The variations in interaction length, characteristics of separation bubble and shock strength for roughened wall were compared to that of smooth wall case. The results show that shock strength decreases for rough wall simulation compared to smooth wall simulation. The shock location moves upstream as the wall roughness increases. Flow separation - reattachment distance decreases for a rough wall compared to smooth wall case mainly due to the decrease in pressure gradient across the shock. The rough wall produce much higher turbulent kinetic energy along the wall surface and this cause the flow variations to propagate more distance downstream of the shock position.