An off-gas treatment system is a vital component of smelter roaster processes as it ensures operation is in accordance with environmental regulations in terms of hazardous emissions. It is, therefore, paramount that a well-designed control structure be incorporated into the system. Analysis of the off-gas treatment processes for a roaster using a systematic control design procedure to provide the necessary verification to current industrial practices for controlling these processes was carried out. We approached this by conducting a topdown (steady-state) analysis based on an available nonlinear model of the process. The results provide insight into, and potential improvement of, the control of the off-gas system. Through designing the bottom-up structure, a feedback control structure was developed to give robust and effective control in terms of disturbance rejection capabilities. The proposed control structure provides for improved performance in an easy form to implement.