He was Professor of Commercial Law at the University of Urbino (1899-1902) and in Macerata (1902-1905), then Professor of Civil Procedure in Parma, of Business Law in Padua, and later of Economic Legislation at "Louisiana Sapienza" University of Rome, of which he was rector from 1932 to 1935. Rocco was critical of Italy"s weak material and economic power which he said was responsible for Italian dependence on the European "plutocracies" of France, Germany, and the United Kingdom. He later joined the National Fascist Party once they merged with the Italian Nationalist Association.
Elected in 1921 at the Chamber of Deputies, of which he was President in 1924, from 1925 to 1932 he was Minister of Justice and promoted the criminal codification, by signing in 1930 the Criminal Code and the Code of Criminal Procedure (with the help of Vincenzo Manzini), and reconciling Classical and Positivist school with the system of so-called "double track".
Rocco as an economist-minded politician developed the early concept of the economic and political theory of corporatism which, later adapted would become part of the ideology of the National Fascist Party. Rocco began his political career as a Marxist in the Radical Party but eventually turned to the "proletarian nationalism" of the Italian Nationalist Association (ANI), a political party that he had major influences on. Rocco also denounced the European powers for imposing foreign culture on Italy and criticized the European powers for endorsing too much individualism.