Experiments are carried out to document the characteristics of a leading-edge separated boundary layer over a rough model surface for a Reynolds number (Re) of 20000, based on the leading-edge diameter (D) and the tunnel velocity (U_∞). Boundary layer and surface pressure measurements are made using a single-sensor, hotwire probe and Scanivalve pressure scanner respectively. Apart from the measurements made on the rough surface model (case-II), flow over the smooth surface model (case-I) have also been documented for a better understanding on the consequences of roughness on the shear layer development. The bubble parameters such as the onset of separation and transition, and the reattachment locations identified from pressure measurements are in good agreement with hotwire data. The primary instability analysis shows that the flow transits from laminar to turbulent through Kelvin−Helmholtz (K−H) instability mechanism for case-I, whereas, it is bypassed in case-II. Though, the mean velocity profiles within the separated region are comparable upto 60% of its respective bubble length (l_b), the thickness of the boundary layer is slightly higher for case-II compared to base case.