Born Rosanna Mullins in Montreal, Leprohon began writing at an early age. In 1846, while she was still attending a convent school, her first poems appeared in the Literary garland. Over the next five years, she had five novels, 15 poems and one story published in this magazine. Her marriage to Jean-Lukin Leprohon, a francophone physician, and the demise of the Literary garland in 1851 signalled the end of this stage in her career.
During her early married years, Leprohon's creative output dwindled to only an occasional poem. However, by 1859 she had resumed writing, and her novel Eveleen O'Donnell was serialized in The Pilot, a Boston journal. The novel for which she is best known, Antoinette de Mirecourt, or, Secret Marrying and Secret Sorrowing, was published in 1864. This work is the second in a series of three of Leprohon's most popular and critically acclaimed novels. While her earlier works have non-Canadian settings, these novels are set in Quebec and effectively depict Québécois history and culture. The French translations of these and other works by Leprohon were well received by francophones.
Mother to 13 children, Leprohon maintained a prolific writing career. Until her death in 1879, her work appeared regularly in the Family Herald, Canadian Illustrated News and L'Ordre.
— "The Stepmother". — The Literary garland. — (February-June 1847). — ISSN 08345406
— Antoinette de Mirecourt, or, Secret marrying and secret sorrowing. — Ottawa: Carleton University Press, 1989, c1864. — ISBN 0886290929 (bd.). — 274 p.
— Armand Durand, or, A promise fulfilled. — Ottawa: Tecumseh Press, 1994, c1868. — ISBN 0919662463 (bd.)
— The poetical works of Mrs. Leprohon. — Montreal: J. Lovell, c1881. — 228 p.