He is best known for his discovery of, and subsequent excavations at, the Lower Palaeolithic site of Boxgrove Quarry in southern England.

[1] He has twice been awarded the Stopes Medal for his contribution to the study of Palaeolithic humans and Pleistocene geology,[2][3] and in 2021 was made an Honorary Fellow of West Dean College of Arts and Conservation.

In 1993, the project unearthed remains belonging to a Homo heidelbergensis, the earliest known hominin in Europe at that time.

The results of these excavations were published in numerous articles and two English Heritage-funded monographs (1999 and 2020),[6][7] and Roberts' experience of the excavations explored in the innovative archaeological (auto)biography Fairweather Eden (1998), co-written with fellow Sussex archaeologist Mike Pitts.

[5][8] Other work by Roberts includes several excavations on the West Sussex downs, notably at Goosehill Camp on Bow Hill, an Iron Age enclosure previously excavated by the Sussex antiquary J.R. Boyden,[9][10][11] and Downley, the location of Iron Age and Roman settlements and a Tudor hunting lodge.