A native of Lake Bluff, Illinois Rockwell studied at the Pasadena Playhouse, from which he obtained a master's degree. During World War II he enlisted in the US Navy for four years serving in Washington D.C. Dramatic roles often eluded him, however, after beginning his career as a contract player for Republic Studios he appeared, over his almost 50-year acting career, in more than 350 television episodes and, on stage, opposite José Ferrer in the 1946 Broadway production of Cyrano De Bergerac, and with Ginger Rogers during the 1960s in a San Diego production of Whitfield Cook's play A More Perfect Union. He appeared in a 1959 Perry Mason episode “The case of the Deadly Toy” as love interest to the defendant Claire Allison as Dick Benedict. He also starred in the 1961 Perry Mason episode "The Case of the Misguided Missile" as an Air Force officer court-martialled on a murder charge. He later starred in the 1962 Perry Mason episode "The Case of the Lurid Letter" as Everett Rixby, a high school principal.