About rock and roll as vocation
About a rock and roller
.. and rock and rollers.
Only one-third about rock and roll...
I wouldn't say I agree with "S & D & R&R" as a philosophy - seems a bit limited. If I was doing the song, I would append another fifteen things at least, including walks in the country, cups of tea, books, curry, and a bunch more, which would spoil the scansion and generally undermine the rock'n'rollness.
Mind you, Ian himself doesn't even agree with the "is all my brain and body needs" bit, because he devotes a whole verse to style - "every bit of clothing / ought to make you pretty" - as one of the bare necessities.
That's my favorite bit actually: "See my tailor / He's called Simon / I know / It's going to / Fit"