The school owes its name to Miss Henry’s grandfather, Andrew Royce, a well-known nineteenth-century Congregational minister in Vermont. As such, the Royce Family crest inspired the school's blue and gold colors and the motto “fortis et prudens simul,” or strength and careful judgment. The school primarily catered to the affluent and societal elites, such as the Elizabeth Campbell, the granddaughter of Judge Elbert H. Gary who was one of the founders of U.S. Steel.
The building reflects the faith in education that characterized the upper and middle classes in the Progressive Era. Many progressives believed that crowded urban living led to unhealthy lives and often attributed this to the perceived character flaws of the poor. Those who could afford the opportunity to live in the suburbs generally abandoned the grand homes in the center of the city during the early 20th century. There, they designed new homes that that allowed for plenty of windows and outdoor space. This belief in the importance of sunlight and fresh air can be seen in this building as the school's founders asked architect Lawrence Buck to make sure that the schoolrooms were would receive natural light and fresh air.
Julia Henry continued played a pivotal administrative role until she died during the 1919 influenza pandemic. Roycemore opened as a co-educational institution, but the school only admitted girls to the upper grades. By the 1930s, the school transitioned to a non-profit private school that was only open to girls. This policy change in 1962 when boys were again allowed into the school. However, it was not until 1968 for the school to graduate the first boy (in a class of five girls and one boy).
In 2011, the school moved to a new location. Today, the school enjoys a much different demographic landscape than when it was founded. As of 2018, the student body consisted of 52% boys, 48% girls and more than half its student body are non-white.