There are at least two Roger Christians that I know of.
The first was a hot-rod DJ and lyricist, who co-wrote songs (usually with Brian Wilson and/or Jan Berry, and occasionally Mike Love) for the Beach Boys and Jan and Dean. He was responsible for the lyrics to, among other classics of early 60s pop, Don't Worry Baby, Little Deuce Coupe, Shut Down, The Little Old Lady (From Pasadena and (uncredited) Surf City. He also worked on lesser known surf/hot rod tracks like Masked Grandma by the California Suns
The other Roger Christian is the director of possibly the worst film ever made - Battlefield Earth, based on the book by L. Ron Hubbard and starring John Travolta. He also apparently worked on The Phantom Menace.