A process for the recovery of metal oxides from a solution containing metallic salts by spray roasting of these solutions. The process is particularly suitable for spray roasting spent pickling acids. The process feeds the solution to a reactor for spray roasting of the droplets in at least two stages, where at least one evaporation stage follows at least one conversion stage to convert the metal salts to metal oxides. The device for implementing the process includes a spray roasting reactor having a first heating zone to evaporate the water and a second heating zone to convert the metal salts to oxides.