It measures roughly 16 metres north to south and 11 metres east to west, rising only about 0.4 metres above the surrounding ground, yet its presence is distinctive enough to show up as a dark stain on aerial photography.

This is a burnt mound, a type of prehistoric site found in considerable numbers across Ireland and Britain. The prevailing interpretation is that such mounds accumulated through a process of heating stones in a fire and then dropping them into a water-filled trough to bring the water to the boil, possibly for cooking, bathing, or industrial processes such as working leather or textiles. The shattered, heat-crazed stones were then discarded into a heap, which over many centuries of repeated use grew into the low, distinctive mounds we find today. The Rosspile example sits near the headwaters of small streams that drain northeastward towards the River Corock, roughly 100 metres away, which is entirely typical: burnt mounds are almost always found close to a reliable water source. A second burnt mound lies approximately 230 metres to the south, suggesting this stretch of the Corock catchment saw sustained prehistoric use, though exactly when, and by whom, the available evidence does not say.