Neil, I think that Hip-Hop/Rap influenced R&B more than Reggae did, but dancehall Reggae is definitely in the mix.

Azizi, I meant the most innovative influence on Rock, but if you want to expand that to R&B I would say that Reggae had a very big influence on Hip-Hop. This is from the Wikipedia article on Hip-Hop:

Hip hop arose during the 1970s when block parties became common in New York City, especially the Bronx. Block parties were usually accompanied by music, especially funk and soul music. The early DJs at block parties began isolating the percussion breaks to hit songs, realizing that these were the most dance-able and entertaining parts; this technique was then common in Jamaica[9][10] and had spread via the substantial Jamaican immigrant community in New York City, especially the "godfather" of hip hop, the Jamaican-born DJ Kool Herc.