Ryan will take over the role Matron "Mama" Morton from the current Mama, Lillias White. Ryan last rejoined the Broadway company of Chicago on March 15.

The show currently stars music star Usher, who has stirred up excitement at the box office and on West 49th Street, where adoring crowds have gathered nightly, causing Chicago producer Barry Weissler to hire additional security guards.

Usher's first performance on Aug. 22 resulted to a daily wrap on Aug. 23 of $200,000 (the average for this time period is $40,000). On Aug. 24 and 25, the take was more than $150,000.

An extension of Usher's stay is a possibility. He is currenly contracted through Oct. 1.

Chicago currently stars Bianca Marroquin, Brenda Braxton, Kevin Chamberlin and R. Lowe, in addition to White. Roz Ryan made her Broadway debut in the Fats Waller revue Ain't Misbehavin'. She also starred on The Great White Way in Dreamgirls and One Mo' Time and in the national tours of Annie, South Pacific and Blues in the Night. Ryan's film credits include "Went to Coney Island," "Cotton Club" and "Dark Indigo."

Chicago won the Tony for Best Revival of a Musical in 1997 as well as awards for actors Bebe Neuwirth and James Naughton, director Walter Bobbie, lighting designer Ken Billington and choreographer Ann Reinking. The original production was directed and choreographed by the late Bob Fosse.

The Ambassador Theatre is located at 215 West 49th Street.