Things are getting dark for Ashlee Simpson-Wentz!

The 25-year-old -- who was fired from Melrose Place because, sources tell, she couldn't act -- likely switched up her hair for her new job. has confirmed Simpson-Wentz is set to play Roxie Hart in the Broadway production of Chicago, starting in December for six weeks.

More cause for celebration: Her son Bronx turns 1 on Nov. 20.