Born at Croxton Park, Norfolk, in 1680, Roger Long was admitted as a sizar at Pembroke College on 4 March 1697. He graduated BA in 1701, was elected Fellow in 1703, and graduated MA in 1704. He was ordained deacon at Lincoln in 1716 and priest at Norwich later that same year. He was rector of Overton Waterville, Huntingdonshire (a Pembroke College benefice), from 1716 to 1751, then of Bradwell-on-Sea, Essex. He had become DD in 1728, and was appointed vicar of Cherry Hinton, Cambridgeshire in 1729, the same year he was elected a fellow of the Royal Society. His main work was 'Astronomy in five books', the last 3 volumes of which were published posthumously.

Long was Master of Pembroke from 1733 to 1770 and Vice-Chancellor of the University of Cambridge in 1733–4. He was elected the first Lowndean Professor of Astronomy and Geometry in 1750.