He competed for the United States in the 1928 and 1932 Summer Olympics; in the 1932 games, held in Los Angeles, he won the silver medal for the shot put.
Rothert earned his bachelor's degree from Stanford in 1930, and a law degree, also from Stanford, in 1937. He practiced law in San Francisco, and taught at Stanford Law School and Hastings College of Law. During World War II, he spent two years in the Marine Corps.