This is a ring-barrow, a type of funerary monument generally dating to the Bronze Age or Iron Age, consisting of a low central mound or flat area enclosed by a circular or oval ditch and an outer earthen bank. The overall effect is subtle; these are not the dramatic cairns of the west coast but intimate earthworks that reward close attention.

The barrow at Ballynamrossagh is oval in plan, measuring roughly 4.5 metres north to south and 3.7 metres east to west. Surrounding it is a fosse, the ditch that defines the inner edge of the monument, about two metres wide and still some 0.2 metres deep, with an outer bank beyond it that measures over three metres in width. Modest figures, but the earthwork has survived in reasonable condition, remaining well preserved almost all the way around, with the exception of a stretch running from the south-south-west through west to west-north-west where erosion or disturbance has softened the profile. The monument sits to the south-west within a larger enclosure, a relationship that raises quiet questions about sequence and intention that the ground itself does not answer. Three mature thorn trees have taken root on the bank in the western sector, hawthorns most likely, which have a long association with sacred or liminal places in the Irish landscape and whose roots have become part of the monument's texture over generations.