Since this was a while ago, I'm going to guess that you've solved the problem, but just incase not, or for other people's info...
You don't want to sing an actual rock song, as I'm sure you know. You want something from a rock musical. Look at music from shows like Hair, Rocky Horror Picture Show, Spring Awakening, or Next to Normal. Choose a song that is fitting for the part you want or your vocal range. So if you wanted to play the part of Judas, Annas, or Herod, you would look for Tenor songs like Donna from Hair, or Run Away With Me from Next to Normal, depending on the time period that is closest to the time period of the show you are auditioning for. In this case it would be Hair.
If you want to sing a rock song, look for a jukebox musical like Tommy, all Who songs, or American Idiot, all Greenday songs.
It's not as hard as people make it sound, and it's easier to find songs that aren't generic or overdone because people aren't suggesting the same old songs to you. coughwickedcough.
Hope this helped someone!