We investigate the boundary-roughness effect on nematics induced by a grooved surface based on two models composed of a lower grooved surface with homeotropic anchoring and an upper flat surface with planar anchoring, and the director at the upper surface is either perpendicular to the direction of grooves (model I) or parallel to it (model II). By comparison, we find that the effect of roughness on model II is larger than model I, which results from the twist deformation in model II. The effective anchoring strength in model II increases with the value of K-2/K-1. Moreover, the free energy of model I is lower than that of model II for nematics with K-2/K-1.