A ringfort, or rath, is a roughly circular enclosure defined by an earthen bank and ditch, typically dating from the early medieval period and used as a farmstead or defended homestead. The unusual thing about the Roolagh example is that the two enclosures share a single fosse, the ditch that surrounds them both, making the arrangement a conjoined pair within one continuous boundary. It is a relatively uncommon configuration. The more unusual thing still is that none of this is visible from the ground any longer.

The antiquarian Thomas Johnson Westropp recorded the site in 1911 to 1912, noting the two forts enclosed within that shared fosse, with the larger of the pair lying to the north and measuring approximately 160 feet by 115 feet. Before that, the site had been marked on the first edition Ordnance Survey six-inch map, which places the conjoined plan on record in the mid-nineteenth century. By the time more recent fieldwork was carried out, the earthworks had been reduced to the point where nothing registers at ground level. What was once substantial enough to map and measure has since been absorbed entirely into the surrounding upland landscape, leaving a site that exists now mainly as a cartographic and archival memory rather than anything a visitor could trace with their feet.