Born to william and Margaret Frances Brown McLennan, Stella grew up in Nebraska City, Nebraska, graduating from St. Joseph's Academy. She attended the Art Institute of Chicago for five years earning her certificate from there in 1908 and the Omaha Institute. She married shortly after graduating from the Chicago Art Institute. She and her mother were vacationing in Portland, Oregon, and Stella received an offer through the Art Institute to teach at a large hacienda near Durango, Mexico. She accepted that position and spent two years in New Mexico. After moving to Tucson in 1918 Roca became a key member of the arts community. She exhibited in 1920 at the Moore & O’Neall Congress Street Bookstore. In 1920 Roca was in a car accident, in Oklahoma City, that killed her husband. Throughout the 1920s she and her son Paul Roca traveled the American West Coast and Mexico. She was inspired by the landscapes of Arizona and Old Mexico and took up painting.