Well, this isn't very specific, but from what I can tell:
Bat Boy/Edgar: Rock Tenor (probably up to like a B flat or so) Meredith: Either Mezzo or Soprano with a good belt Dr. Parker: High Baritone or Tenor. It only goes up to F sharp I think, but it has a high tessa tura Shelley: Soprano Sheriff: Character baritone
And the rest of the roles are all pretty high. Pretty much all the men in the show need to have excellent high ranges, and the women too. Hope that helps some!
If you read the script, there's an introduction that says it can have as many as 100 people in the show or as little as 10. It just depends on the size of your theater company or how they want to stage it. I saw a video (coughyoutubecough) of Nebraska State University that did it and they had like 50 people on stage for "Comfort and Joy" and I have to say it looked horrible.
What about Rick? Doesn't he have a pretty high range as well?
I am getting ready to reprise my role as Bat Boy and step in as the director here in just a few weeks. Here is the list of all of the characters in the show, how I split them up anyways. It can be done a number of different ways.
Bat Boy (Tenor with a very large range...up to a high C) Shelley (Soprano) Meredith (Alto) Dr. Parker (Bari-tenor) Rick Taylor/Lorraine (Tenor) Ruthie Taylor/Ned (Alto) Ron Taylor/Clem (Alto...but I have a girl playing the role) Mrs. Taylor/Mayor Maggie (Alto) Sheriff Reynolds (Baritone) Billy Hightower/Roy/Mr. Dillon/Institute Man (Baritone) Pan/Bud/Daisy (Tenor)
Comfort and Joy and Joyful Noise Reprise are the 2 that stick out. They are written high, but I have heard them taken down and it didn't sound too bad. What's your range?