M. Edgar Rosenblum, managing director of New Haven’s Long Wharf Theater during the tenure of artistic director Arvin Brown from the late 1960s to the ’90s, has been tapped as administrative producer at the Berkshire Theater Festival.He will work with Kate Maguire, executive director of the summer theater located in the Massachusetts Berkshires. Rosenblum was chairman of the board of trustees of the American Arts Alliance. He also was founding president of the National Corporate Theater Fund. He continues to serve as consultant for the Rubicon Intl. Theater Festival in Ventura, Calif.