Singer-songwriter Roger Miller, whose tune “King of the Road” was a 1965 hit with both country and pop music fans, died of cancer Sunday at age 56.Miller died at Century City Hospital after battling the disease for a year. The singer had announced in January that he was undergoing radiation treatment for a cancerous tumor below his vocal cords. Miller’s wife, Mary, and his son, Roger Dean Jr., were at his side when he died. Miller won 11 Grammy Awards and received a Tony for the Broadway musical “Big River,” based on Mark Twain’s “The Adventures of Huckleberry Finn.” The 18 songs Miller wrote for “Big River” represented his first effort at writing for the stage. It won seven Tony Awards in 1985, including one for best musical score, and ran on Broadway for 2 1/2 years. In addition to his wife, Miller is survived by seven children and seven grandchildren.