We conduct computations of rotating Rayleigh-Bénard convection in the so-called geostrophic regime, characterized by strong thermal forcing (high Rayleigh numbers) and strong rotation (small Ekman numbers). We employ the full Navier-Stokes equations in our computations and compare no-slip and stress-free boundaries for the plates. The Ekman boundary layers, that exist in the no-slip case but not for stress-free, enhance convective heat transfer and prevent the formation of large-scale flow structures.