This numerical simulation of a roughened solar air heater (SAH) is an investigation of its thermo-hydraulic performance using CFD techniques. The two-dimensional geometry of the SAH, including the absorber plate with roughness elements, is modeled using ANSYS 18. The effects of rib height and rib spacing, on the heat transfer and pressure drop characteristics of the solar air heater are investigated in turbulent flow regions, Re varying between 4000 and 16,000. The numerical simulation provides detailed information on the flow patterns, temperature distribution, and heat transfer rates within the SAH. The results of the simulation show that the decreasing rib spacing and increasing the rib height improve the SAH's ability to transmit heat. The simulation results provide valuable insights into the optimal design parameters for roughened SAHs.