Ronell was, along with Dorothy Fields, Dana Suesse, and Kay Swift, one of the first successful Hollywood and Tin Pan Alley female composers or librettists. She cowrote Disney's first hit song, "Who's Afraid of the Big Bad Wolf?" (1933) with Frank Churchill for the cartoon of the same name.
She wrote the lyrics and music for the Broadway musical Count Me In (1942) She wrote songs for movies including Champagne Waltz (1937) and Blockade (1938) and wrote the scores for movies including the Cowan produced The Story of G. I. Joe (1945), the film adaptation of the Weill/Nash musical One Touch of Venus (1948), and the Marx Brothers Love Happy (1949). She served as musical director for Main Street to Broadway (1953). She was nominated for Best Song, "Linda," and with co-composer Louis Applebaum for Best Score, for her work on The Story of G. I. Joe.
Ronell was romantically involved with George Gershwin at the time she wrote her most famous song, "Willow Weep for Me" and speculation in the New York City composer community is that Gershwin actually wrote the song and gave her the copyright as a gift. However, this has never been proven and is still, at this point, based on the striking similarities in the song to the blues-inflected style of Gershwin.