To what extent did the USA attempt to 'roll back' communism, rather than merely contain it, in the period 1950 to 1985?
It is perhaps easier to argue that the US policy during this period was one of containment. While the US vigorously sought to keep communism from spreading, American strategy generally stopped short of attempting to destroy the institution where it had become established in the wake of World War II. President Truman, for example, opted not to expand the Korean Conflict into China, and Eisenhower chose not to actively support the Hungarian uprising in 1956. Essentially, by 1950, the United States and the Soviet Union were reluctant to pursue an overly-aggressive program in Europe out of fears that nuclear war would result.
As the Cold War progressed, however, the United States did try to support anti-communist leaders, including rebels in various developing countries. This was especially the case in Latin America, and examples include numerous attempts to overthrow and perhaps even assassinate Fidel Castro (the Bay of Pigs fiasco was the most conspicuous of these attempts.) Additionally, beginning with the Reagan presidency, the United States adopted a stance of bringing about the destruction of communism through massive military spending and supporting Mikhail Gorbachev's reforms within the Soviet Union itself.