Radio waves, along with any type of radiated electro-magnetic wave, all travel with the same velocity which is the speed of light in that particular medium. The only difference between radio waves and microwaves is the frequency of oscillations of the energy in the wave. One way to change the speed on a very small scale is to change the medium in which the wave travels because the speed of light varies from one medium to another. For instance it moves slower in water than air. Frequency has some effect on the speed of the wave in any medium other than a vacuum, however this very small effect is normally neglected in simple calculations.