Well I wasn't around in the 60s and only part of the 70s but I don't think it was just about challenging conformity myself (although that was part of it), rock and roll gave a voice to teenagers where they didn't have one before. You have to remember that the popularity of rock and roll was a symptom of a youth culture that didn't really exist before WWII. Post-war, there was a rise in affluence in the 50s that meant teenagers had more free time and money to spend on music, movies and clothes that allowed them to express themselves and as a new force in the marketplace that meant they had a much bigger influence on social change . In particular I would say that the protest music of the 60s had a significant impact on American society and that was certainly driven by youth culture (if teens hadn't been buying Bob Dylan's records he wouldn't have been on TV, giving a platform for his anti-war views etc) . It rallied people together and expressed a common view. There's a pretty good article on it here:
http://news.bbc.co.uk/1/hi/world/americas/4498011.stm
I don't know if I've helped at all, or just sprouted obvious stuff but I tried
