In 1942 Roberts married Marian Ann Evans, daughter of David and Elizabeth Evans of Robertstown, Aberdare. They had two children: a daughter, Ann, and a son, Dafydd. Marion Goronwy-Roberts wrote a biography of Marion Phillips, the pioneering Labour campaigner for women's rights, and a number of books in Welsh, including the centenary lecture at the 1981 Welsh National Eisteddfod on the Welsh poet, scholar and politician, W. J. Gruffydd.
