The aim of this paper was to determine the aerodynamic forces on a rotating circular cylinder immersed in a two-dimensional and incompressible flow at high Reynolds numbers and low rotation rates. A lagrangian mesh-free vortex method is used, where Lamb vortices are generated at every time step. The convection of the vortices is simulated using a first order time marching scheme and diffusion is simulated using the random walk method. The aerodynamic forces, calculated from the Blasius equation, show acceptable agreement with others available in the literature. The main conclusion is that the method is able to predict separation, vortex shedding, and classic and inverse Magnus effect.