As nouns the difference between reggae and rasta

is that reggae is a form of music originating in Jamaica and associated with Rastafarianism, featuring a heavy bass line, percussive rhythm guitar on the offbeat, often with close vocal harmonies while rasta is belonging to an originally Jamaican sect regarding Blacks as chosen people, and the Jamaican national colors and the leaf of the marijuana plant as symbols.

As a proper noun Rasta is

rastafari.