Three large thorn trees grow at the site, and until 2011 the monument passed entirely unrecorded. What lies here belongs to one of the rarest categories of prehistoric structure in Ireland: a radial-stone cairn, a form so scarce that only twenty examples are currently known across the entire country.

A radial-stone cairn consists of stones set outward from a central point like spokes, defining the edge of a circular cairn, which is essentially a mound of stones used as a funerary or ritual monument. The type is generally associated with the later Bronze Age stone circle tradition of south-west Ireland, which makes the Galway examples geographically notable outliers. The Rooghaun monument had an internal diameter of roughly 16 metres north to south. Only the eastern half of the circle now survives, comprising sixteen stones averaging between 0.50 and 0.70 metres in height, spaced roughly 1 to 1.60 metres apart. Several are displaced or leaning. Between some of them there is cairn infill, rubble packed in to consolidate the structure, and the interior is grassy but stony underfoot, suggesting that cairn material once spread across the enclosed area. On the western side, a single large stone lies flat and may once have stood upright as part of the circuit. A raised, stony area on the same western side resists easy interpretation: it could be an original feature of the monument, the result of later land clearance, or the collapsed remains of the western arc of stones. A second example of the monument type exists in County Galway at Cartron South, some 23 kilometres to the south-east, making Rooghaun part of a very small and poorly understood regional cluster of a monument type that archaeologists are still working to define.