This study aims to optimize a Trombe wall by integrating rectangular artificial roughness, comparing three surface configurations with different rib heights to a smooth wall. Two-dimensional numerical simulations were carried out to analyze the flow and heat transfer in the air gap of a Trombe wall equipped with transverse rectangular roughness. Air circulates by natural convection, and the absorber wall is uniformly heated. The problem was modeled using the CFD code ‘Fluent’, based on the finite volume method, allowing the resolution of both air flow and heat transfer in the studied domain. To complete the transport equations expressing the conservation of mass, momentum, and energy, the k-ω SST turbulence model was used. To examine the flow and heat transfer in the region between two successive ribs, a structured mesh was chosen, dense near the walls and slightly coarser elsewhere. The effect of roughness parameters on the convective heat transfer coefficient, air ventilation rate, and thermal efficiency parameter was studied. The results clearly show an improvement in convective heat transfer and therefore the thermal efficiency of the Trombe wall.