[1] Romanus worked as a law clerk in the Svea Court of Appeal in 1929, became an assessor in 1939, and was director in the Ministry of Justice from 1944 to 1947.

Romanus was appointed Hovrättsråd in 1946 and was a member of the Swedish state legislative committee (Lagberedningen) from 1947 to 1950.

He was notary and secretary in various Parliamentary committees in the Riksdag from 1936 to 1942, a substitute in the Labour Court (Arbetsdomstolen) in 1941 and vice chairman from 1949 to 1950.

[1] Romanus was assigned to the Ministry of Ecclesiastical Affairs and in Ministry of Justice from 1941 to 1943, was secretary of the 1941 års befolkningsutredning ("1941 Population Survey") from 1941 to 1944, the Parliamentary Investigation Commission (Parlamentariska undersökningskommissionen) from 1945 to 1947, and served as Deputy Justice Ombudsman from 1948 to 1949.

[1] Furthermore, Romanus was vice chairman of the Swedish Press Council from 1956 to 1959, chairman there from 1960 to 1976, chairman of the Swedish Youth Correctional Board (Ungdomsfängelsenämnden) from 1958 to 1969, of the Council on Legislation from 1962 to 1964, of the Kommittén för lagstiftning om yttrande- och tryckfrihet ("Committee on Legislation on Freedom of Expression and Press") from 1965 to 1972, if the Massmedieutredningen ("Mass Media Investigation") from 1970 to 1976, of the Programrådet för radioaktivt avfall ("Radioactive Waste Program Council") from 1980 to 1981, and of the Nämnden för hantering av använt kärnbränsle ("Committee for the Management of Spent Nuclear Fuel") from 1981 to 1984.