Rietti worked as a researcher at various Argentine universities and state agencies including the Department of Inorganic Chemistry and Physicochemistry at the University of Buenos Aires between 1955 and 1956. She was also a member of the board of directors of the Faculty of Exact and Natural Sciences of the University of Buenos Aires (UBA), where she witnessed the country's security forces breaking into the university during the events known as the Night of the Long Canes on 29 July 1966.
On that night, after police detained about 400 intellectuals, Sara and her husband Víctor moved from one police station to the next to free their colleagues from jail. As a result of the nationwide repression, numerous laboratories and libraries were destroyed and many scientists and academics were exiled or fled the country. Sara and Victor decided to remain in Argentina.
Rietti worked at the Latin American Publishing Center as director of the Scientific Collection between 1967 and 1969 and served on the board of that publisher between 1972 and 1992. Between 1973 and 1975, she was the coordination director of the National Institute of Industrial Technology.
In 1983, when science was again allowed to flourish in Argentina, the mathematician Manuel Sadosky appointed her Chief of Staff of the Secretary of Science and Technology, over which he presided, and in 1994 she was appointed academic coordinator of the Graduate Policy and Management of Science and Technology at the UBA. She was also a teacher advisor to the Rectorate there, a position she held until the end of her life.