Not so fast yo.. early Rock and Roll as definitely a huge influence on the early 1960s rock steady-ska-reggae scene! Indeed, dividing those three into a different genre is a bit disengenuous because in actuality it was THE SAME musicians making all three!
You are right about many things, but to negate the influence of rock and roll I think is off-base here. Its not that rock an roll was the major influence, but it was still very relevant.
Today Rap music is the Lakers