He was an intellectual member of the NSDAP, and also a member of the Cabinet Hitler. He was one of the major developers of the racist theories of the Nazis. His most important work was Der Mythus des zwanzigsten Jahrhunderts (English: The Myth of the Twentieth Century, published in 1930), which became a standard for Nazi Germany.
During the war he was minister for Eastern Europe affairs.
Rosenberg was one of the 24 accused of the Nuremberg Trials and because of war crimes sentenced to death. In October 1946 he was hanged. At the Nuremberg Trials it appeared that none of the accused had read his above mentioned book.