To many butterflys in music to really predict. Rock and rolls abscense would either be a minimal effect, grow popular later, or lead to a dramaticaly affect culture.
Personally I believe music has profound impacts on culture wheter we believe so or not. I imagine a lack of rock prevents the development of other types of music such as rap, country, heavy metal, techno, etc. Or at least makes them dramatically different (ie. country would be more folksy than it already is, rap would be more jazz oreinted)
Sexual Revolution is delayed at least...
American Music would be dominated by jazz, swing, and big band until at least the 60's or 70's. It would have some crazy branches though, especially a branch influenced by the drug revoltuoon of the 60's. Also I see Spanish Salsa and Latin music growing in popularity as the new big music "import" will be from Mexican and Latin American immigrants.
Many cultural changes would probably happen (interseting to see where the rural areas, south, and "redneck" areas would be without country music culture, same for inner cities and black areas without rap and hip-hop.) but I do doubt there would be many political changes, not yet at least. Remember, everyone in charge still lived in the swing-big band era, rock was only just devloping.