Not all rock and roll, but some classic opening lines in songs that come to mind...
A child arrived the other day, he came to the world in the usual way.
Early one morning while making the rounds, I took a shot of cocaine and I shot my woman down.
Breaking rocks in the hot sun, I fought the law and the law won.
Your momma's in the back seat, telll her to push over and move them big feet, every monday morning i gotta drive her down to the unemployment agency.
Jesus hangs behind the glass above venetian doors, his window box boasts crimson flowers fresh cut the day before.
I think Maggie May might be the best opening line, but someone already has posted that one.