Joe Dirtamancer is a Dirtamancer in the Magic Kingdom. He is Qualified, meaning that he can sit in judgment of other Casters in an enforcement council. He describes himself as a 'rocker.' This is likely an affirmation of his status as a Dirtamancer, but may also refer to his position as a Qualified. He is responsible for the destruction of the barrier that Sizemore Rockwell constructed in the Magic Kingdom.
Real World References
Joe Dirt is a movie starring David Spade, whose character strongly resembles the Dirtamancer.