In 1927, Rosseland earned a PhD. from the University of Oslo. As a professor at the University of Oslo from 1928 to 1964, he built up and headed academics at the Institute of Theoretical Astrophysics (Institutt for Teoretisk Astrofysikk). Rosseland was a key participant when the University of Oslo built the Institute of Theoretical Astrophysics in 1934, using funding from the Rockefeller Foundation. Between 1929-30 he was a guest professor at the Harvard College Observatory. In 1934 he founded the journal Astrophysics Norvegica, published by the Norwegian Academy of Science and Letters. In 1936 he published his textbook Theoretical Astrophysics, which contained numerous original contributions. Rosseland was instrumental in the effort behind the building of the Oslo Analyzer, finished in 1938 and for four years the world's most powerful differential analyzer.[4][5]
Rosseland returned to Norway in 1946. In the postwar period he was involved in the development of the Norwegian research policy and was among those involved in the creation of the Institute for Energy Technology which was established in 1948 and Norwegian Academy of Technological Sciences which was founded during 1955. He was also the driving force behind the creation of Harestua Solar Observatory located at Gunnarshaugen in Oppland, which was inaugurated in 1954.[7]
Rosseland was Norwegian delegate to the CERN Council in the early days of the organization.[8]