Plasma rotation is thought to play an important role in the stability properties of tokamak plasmas. Hence it is relevant to accurately predict the rotation properties of ITER plasmas. Because of the finite number of Toroidal Field (TF) coils, a toroidal variation (ripple) of the main magnetic field exists in Tokamaks. Ferrite material will be mounted between the ITER coils in order to reduce the ripple. Nevertheless, the estimated TF ripple in ITER is in the order of d~0.5% at the outer separatrix while this value in JET is only d~0.08%. A larger TF ripple will have a non-negligible effect on the plasma rotation. In order to extrapolate rotation properties of present experiments to that of ITER plasmas, toroidal field ripple effects should be understood. The TF ripple could affect the toroidal plasma rotation in two ways. Firstly, rotation can be reduced by friction between the circulating particles and those locally trapped in the toroidal field ripple. Secondly, the TF ripple causes diffusion of the banana orbits of high-energy trapped particles in radial direction. This radial ion flow induces a j¥B torque on the plasma. The toroidal torque due to ripple banana orbit diffusion is in counter-current direction. The first effect tends to relax the plasma rotation to zero, while the second mechanism could drive rotation in counter-current direction. This has been observed in JT-60U where, with near perpendicular Neutral Beam Injection (NBI) and, hence, little NB driven torque, significant plasma rotation in counter direction was measured in the presence a TF ripple of d~1%. Rotation in co-current direction was observed after the TF ripple was reduced using Ferrite inserts.