Foster was born on 16 January 1949 in
Waterford, to two teachers: Betty Foster (née Fitzroy), a primary teacher, and 'Fef' (Frederick) Ernest Foster, a teacher of
Irish. His father, Fef, was a native of
Drung, a tiny hamlet and parish located between
Cavan Town and
Cootehill in
County Cavan where Roy's grandfather Frederick Foster signed the
Ulster Covenant in 1912. Roy attended
Newtown School in Waterford, a multi-denominational school that was founded as a
Quaker school in 1798. He won a scholarship to attend
St. Andrew's School in
Delaware for a year before reading history at
Trinity College Dublin. He was awarded an M.A. and PhD by Trinity College, where he was taught by
T. W. Moody and
F. S. L. Lyons, and was
elected a scholar in History and Political Science in 1969. ==Academic career==