In 1959, she transferred from the School of Natural Sciences to the Department of Physical Sciences in the School of General Studies at UPR. In 1961, she was director of a training program for physics high school teachers funded by the National Science Foundation. She was chair of the physical sciences department from 1964 until 1966 when she returned to her position in the School of Natural Sciences. In 1970, Del Rosario was designated Dean of Studies, a position she held until her retirement in 1973.