During 1969–1972, he did postdoctoral research at Harvard University.^[9] before moving to Cold Spring Harbor Laboratory,^[14] where he was hired by James Dewey Watson, a co-discoverer of the structure of DNA and a fellow Nobel laureate. In 1977, he published his discovery of RNA splicing.^[14] In 1992, he moved to New England Biolabs.^[9] The following year, he shared a Nobel Prize with his former colleague at Cold Spring Harbor Phillip Allen Sharp.^[15]

Roberts's discovery of the alternative splicing of genes, in particular, has had a profound impact on the study and applications of molecular biology.^[6] The realisation that individual genes could exist as separate, disconnected segments within longer strands of DNA first arose in his 1977 study of adenovirus,^[14] one of the viruses responsible for causing the common cold. Robert's research in this field resulted in a fundamental shift in our understanding of genetics, and has led to the discovery of split genes in higher organisms, including human beings.