<p>This study investigates the performance of a step slider bearing lubricated with Rabinowitsch fluid considering a rough bearing surface. The influence of surface roughness is analyzed using Christensen’s theory, while the fluid film pressure is determined through an analytical solution of the modified Reynolds equation using the small perturbation method. Based on the fluid film pressure, the lifting force and coefficient of friction are evaluated. To ensure reliability, the model is validated using Response Surface Methodology (RSM), and sensitivity analysis is performed to identify the most influential parameters namely, film thickness, bearing length, and the non-linear fluid factor—on the lifting force and friction. Results indicate that film thickness and bearing length significantly impact bearing performance, while rough surfaces exhibit lower load-carrying capacity and reduced friction compared to smoother surfaces. This work provides a comprehensive theoretical framework for understanding the combined effects of non-Newtonian lubrication and surface roughness on step slider bearings.</p>