What do you think the beginning of rock n' roll was?

I'm doing a project on the history of rock n' roll, and as I'm
actually starting to research, I'm thinking, "oh god, what have I
gotten myself into...?!?!?" there's a lot of opinions as to where the
begining of rock n' roll was, and I don't even know where to start?
Was it with Elvis? Before him? Or was it with the Beatles, and the
Rolling Stones?

So.... help me out? When do you think it was? Can you back it up with
good facts? Whoever does, and convinces me when it really was gets the
best answer.

THANKS SO MUCH!