Richard O'Brien and Richard Hartley
Frank's castle wouldn't be able to function without Riff Raff and Magenta, yet they don't seem to get any respect, because most of what these servants do is behind the scenes. In a similar vein The Rocky Horror Picture Show wouldn't be what it is without Richard O'Brien (who also played Riff Raff) and Richard Harley (who didn't play Magenta).
The two Richards wrote and composed the music for the movie's stage predecessor, the Rocky Horror Show. O'Brien wrote the script and the lyrics while Hartley worked on the musical arrangements. (Source)
Just as the movie itself tackles a series of cheesy sci-fi subgenres, the music, too runs the gamut. There's some classic rock ("Hot Patootie – Bless My Soul"), a pure dance number ("The Time Warp") and a heartfelt ballad that wouldn't be out of place in a mainstream musical ("Rose Tint My World").
The movie wouldn't be the same without the music. Like any good musical, the songs enhance the feelings of the characters, and punctuate major moments in their lives. Brad doesn't just propose, he declares his love with the passionate "Dammit, Janet." And Janet doesn't experience a private sexual awakening, she declares her newfound sexuality with the steamy number "Touch-a Touch-a Touch-a Touch Me."
Because the show was originally only forty minutes long, O'Brien and Hartley added songs on the fly. (Source)
But moving from stage to screen caused a few songs to be eliminated. If you want to hear "Superheroes" or "Once in a While," you have to hunt down special-edition DVDs or Blu-rays of the film. (Source)
You don't need to be a superhero to find it, though. It's readily available on Amazon…and not just every once in a while. (Source)