The 69-year-old Roberts has been hospitalized. St. Luke's-Roosevelt Hospital Center spokesman Jeff Jacomowitz tells The New York Times the actor is in stable condition.
Roberts is known for his roles in Woody Allen movies including "Annie Hall" and "Hannah and Her Sisters." He was last on Broadway in the 2007 musical "Xanadu" (ZAN'-uh-doo).
Meier said understudy Anthony Newfeld would take over Roberts' role at the Sunday evening performance of "The Royal Family," a comedy by George S. Kaufman and Edna Ferber. The Manhattan Theatre Club production opens Thursday at the Samuel J. Friedman Theatre.