Has the author given an official spelling of all the characters' names? The additional cast has just been announced on the
official website, but I'm afraid I'll get some names wrong if I just try to throw wild guesses. (Edit: I found the names spelled similarly on a few websites, no clue if they are indeed official, but I'll go with these for now.)
Announced cast:
Bard ： Hiroki Touchi
Finny ： Yuuki Kaji
Meirin ： Emiri Katou
Tanaka ： Shunji Fujimura
Elizabeth ： Yukari Tamura
Madam Red ： Romi Paku
Grell ： Jun Fukuyama
Lau ： Kouji Yusa
Undertaker ： Junichi Suwabe
There are quite some names here. Along with a relatively unexperienced seiyuu, Yuuki Kaji, whose most important role to date has been Over Drive's Mikoto Shinozaki - but he'll also voice the male lead in Yozakura Quartet this fall, which could mean his career is now set in motion. Also, Shunji Fujimura seems to be an actor who has yet to do any voice work for anime.