John (Johnny) August Emanuel Roosval (29 August 1879 – 18 October 1965) was a Swedish art historian, Medieval ecclesiastical art specialist, and university professor.
Johnny Roosval was born in a bourgeois family in Kalmar, but grew up in from the age of five and went to school there.
He studied at Uppsala University from 1897, and finished his kandidat degree in Philosophy, Latin, French, and Æsthetics with the history of literature and art, and Scandinavian philology in two years.
In 1899 he went to Berlin as a tutor for the son of the Swedish military attaché there, Henrik de Maré. The son, Rolf de Maré, later became known as an art collector and as the owner of the Ballets Suédois. Henrik de Maré's wife, sculptor Ellen von Hallwyl, would later divorce him and married Johnny Roosval in 1907. At the same time, he enrolled at the University of Berlin, where he was a student of Heinrich Wölfflin and Adolph Goldschmidt, two of the founders of art history as an academic discipline. Roosval joined Goldschmidt on bicycle tours of rural churches in the vicinities of Berlin, a method for art historical exploration he would later introduce to his Swedish students. He was awarded his Berlin Dr. phil. degree in 1903 for a dissertation on Flemish altarpieces in Sweden.
Returning from Berlin to Sweden, he worked at the Nordiska museet in Stockholm and also trained as a reserve officer, later teaching at Uppsala University as a docent of art history, newly established as an independent discipline, having previously counted as part of the study of Æsthetics.
He remained in Uppsala until 1914, when he moved to the . There, he received a titular professorship in 1918, was appointed to the Anders Zorn professorship of Scandinavian and comparative art history in 1920, in accordance with the wishes of the donor, the painter Anders Zorn, but transferred to the J. A. Berg professorship of art history and theory in 1930, becoming an emeritus in 1946.