What role did radio play in the explosion of rock and roll and who were the important personalities?

Rock and Roll came out about the time of the Television gaining popularity in the U. S. Television was absorbing the dramas that had previously been on radio. As such, radio was expanding into the music market. One of the pioneer radio hosts was "Moondog" Alan Freed in Cleveland, Ohio is credited with naming this new style of music which was in part derived from R&B music.