In 1998, ahead of construction by Mayo County Council at Coolroe, archaeologists uncovered a fulacht fia, a type of Bronze Age cooking or industrial site found in considerable numbers across Ireland, typically identified by a distinctive mound of fire-cracked stone and charcoal-blackened earth beside a water source. The Coolroe example sat in poorly drained, rush-grown pasture, the ground sloping gently southward toward the Robe River, exactly the kind of wet, marginal ground these sites favour.

The excavation, carried out under licence 98E0389 and reported by R. Gillespie, revealed an oval mound measuring roughly 19 metres by 9 metres and about 0.6 metres deep, composed of heat-shattered stone packed into a matrix of dark, silty clay stained with charcoal. Within the mound were the features that make a fulacht fia recognisable: a rectangular trough measuring 1.9 metres by 1.3 metres, a roughly circular pit or trough about 0.9 metres across, and traces of at least one further rectangular trough less clearly preserved. The working theory for such sites is that stones were heated in a fire, then dropped into water-filled troughs to bring the water to boiling point, whether for cooking, bathing, or some industrial process. The finds recovered at Coolroe support a broadly prehistoric date and hint at a range of activities: struck chert flakes, a flint end-scraper used for working hides or bone, and fragments of antler and bone. Two further fulachtai fia were identified just a few metres to the east of the main mound, and a separate area of prehistoric activity lay roughly 80 metres to the west, suggesting that this stretch of the Robe valley was a focus of repeated use over a long period rather than the scene of a single, isolated episode.