Born in New York City, on March 31, 1935, Judith Louise Perelman was raised in the Bronx. Her father, Joseph Perelman, was a textile official; her mother, Dorothy Shapiro Perelman, was a public schoolteacher. Rossner wanted to be a writer, even before she could read or write, and dictated poems and stories to her "warmly supportive" mother. She was also encouraged by an uncle, the American-Canadian writer Charles Yale Harrison, best known for his best-selling story of World War I, "Generals Die in Bed" (1930). She was Jewish.