This layering of materials, one era's boundary absorbed into another's, is part of what makes a rath worth looking at twice. A rath is a ringfort, the most common monument type in the Irish landscape, built typically between the sixth and tenth centuries as a defended farmstead for a single family or small community. They are defined by a raised bank, or rampart, and an external fosse, which is a ditch dug to reinforce the enclosure. Here, that fosse survives along a generous arc running from the north-north-west, around through the east, and down to the south-south-west.

The enclosure at Carrowroe is subcircular in plan, measuring roughly 42 metres east to west and 39.5 metres north to south. It was noted as early as 1914, when it appeared in a catalogue by Neary, which recorded it as entry number 114. The site was described at that time as being in fair condition, and the stone wall now overlying the original bank appears to be a later addition rather than part of any ancient construction. The gaps visible in the wall are considered modern, suggesting the site has been in continuous agricultural use, with the old boundary simply pressed into service as a field wall, a fate common to hundreds of ringforts across the country.