Sherwood may have received her earliest training in art from her mother; a sketchbook dating to 1873 was in the hands of family members in 1987. Rosina traveled to Europe in 1876–1877, and was presented to Queen Victoria during the trip. Returning to New York, she and her friend Dora Wheeler began study with William Merritt Chase, and by 1881 she took studio space in the Tenth Street Studio Building. Among her earliest works were illustrations for publications such as Harper's Magazine, and in 1880 she won the $1,000 first prize in a competition to design a Christmas card for Louis Prang & Company. Sherwood and Wheeler worked together in the design firm Associated Artists, run by Candace Wheeler, Dora's mother; they designed tapestries, curtains, and wallpaper. Subjects included a variety drawn from American literature.
In 1884–1885 the women attended classes at the Académie Julian in Paris;[2] Sherwood's instructor there was Tony Robert-Fleury.[4]
Rosina married, in 1887, Arthur Sherwood, having five children with him, including future Pulitzer Prize winner Robert E. Sherwood. She continued working after her marriage, often looking to members of her family as her subjects.
Elizabeth Eggleston Seelye's story "“The A.O.I.B.R." appeared in Harper's Bazaar in 1889 with Sherwood's illustration of a child reading. The Rockwell Centre for American Visual Studies cites this as a surprisingly early illustration of a girl reading. The subject of a female reading in this sketch is thought as rare (like the examples in Louisa Allcott's Little Women).[5]
She accepted commissions once more in 1918 to provide support for her family, and continued painting watercolors for much of her career. One of these, 1922's San Pedro, Manila, was included in the inaugural exhibition of the National Museum of Women in the Arts, American Women Artists 1830–1930, in 1987.[2]