Rock ‘n’ roll is the most common spelling for the genre of music, but rock-and-roll, rock and roll, rock-‘n’- roll, rock & roll, and rock’n’roll also appear often. Rock ‘n’ roll has a breezy and colloquial look that reflects the spirit of the music, while rock-and-roll and rock and roll are a little more formal. In any case, there is no right or wrong way to write the term, though rock ‘n’ roll is the most common version and hence the safest.
Examples
Rock ‘n’ roll
Today marks the 52nd anniversary of the tragic plane crash that killed three young rock ‘n’ roll musicians well before their time. [USA Today]
But it won’t be a traditional rock ‘n’ roll memoir. [NY Times]
Rock and roll
Don Kirshner, rock-and-roll impresario [Washington Post]
Rock’n’roll
It’s easy to fall for American rock’n’roll. [Guardian]
Theatre of shameless rock’n’roll [Sydney Morning Herald]