From Bryan Garner’s Usage Tip of the Day, on rock ’n’ roll , rock-’n’-roll , rock’n’roll , rock and roll , rock-and-roll , and rock & roll :
Each of these is listed in at least one major American dictionary.Garner must have had fun writing this entry.
“Rock ’n’ roll” is probably the most common; appropriately, it has a relaxed and colloquial look.
“Rock and roll” and “rock-and-roll” are somewhat more formal than the others and therefore not very fitting with the music itself. The others are variant spellings — except that “rock-’n’-roll,” with the hyphens, is certainly preferable when the term is used as a phrasal adjective [the rock-’n’-roll culture of the 1960s].
Fortunately, the editorial puzzle presented by these variations has largely been solved: almost everyone today refers to “rock music” or simply “rock.” Increasingly, “rock ’n’ roll” carries overtones of early rock — the 1950s-style music such as “Rock Around the Clock,” by Bill Haley and the Comets.
[Bryan Garner, author of Garner’s Modern American Usage (2009), offers a free Usage Tip of the Day. You can sign up at LawProse.org. Orange Crate Art is a Garner-friendly site.]