Detachment of colloidal particles from surfaces in simple shear flow has been studied experimentally and theoretically. It is clearly shown that for molecularly smooth surfaces the elastic deformation of the substrate or the particles does not provide sufficient restraining torque to prevent particle rolling. The presence of asperities roughness) on either the substrate or the particle is a necessary condition to prevent detachment. When such asperities are present the elastic and surface properties of both the substrate and the particle play an important and predictable role in determining the magnitude of the restraining torque, i.e., the critical fluid velocity at which the colloids will be detached.