The generation of nonequilibrium electron spin polarization, spin transport, and spin detection are fundamental in many quantum devices. We demonstrate that a lattice of magnetic nanodots enhances the electron spin polarization in monolayer graphene via carrier exchange. We probed the spin polarization through a resistively detected variant of electron spin resonance and observed resonance amplification mediated by the presence of the nanodots. Each nanodot locally injects a surplus of spin-polarized carriers into the graphene, and the ensemble of all spin hot spots generates a nonequilibrium electron spin polarization in the graphene layer at macroscopic lengths. This occurs whenever the interdot distance is comparable or smaller than the spin diffusion length.