He served overseas in Egypt, Greece, Turkey, Iran and as ambassador at different times to Pakistan, Sudan, South Africa, and Brazil.
After graduating from high school in 1935, Rountree got a job with the United States Department of the Treasury where he held various clerical and accounting positions.
This led to a long diplomatic career in which Rountree specialized in the Middle East and South Asia.
During 1948 and 1949 he was assigned to the U.S. Embassy in Athens, Greece, where he helped administer U.S. aid programs to the Greek army which was fighting Communist insurgents.
In this position he helped develop U.S. policy involving the Suez crisis in November 1956 and the U.S. intervention in Lebanon in 1958.