What makes the site quietly arresting is not its scale but its accumulation of layers: early medieval cross-slabs, a blocked doorway inserted into a wall that was itself built to shorten an already ancient nave, and a holy well roughly 150 metres to the north-east, all gathered around a foundation attributed to one of early Ireland's more widely travelled saints.

The church at Rossinver is associated with Maodhóg of Ferns, known also as Aidan or Mogue, who died in AD 620 or 625 according to the annals. He was descended from the Collas Uais sept of the Oirghialla, and a Life composed probably in the 16th century places him at both Rossinver and Drumlane in Cavan before he eventually settled at Ferns in County Wexford, where he became bishop. His feast day was observed on the 31st of January at both Ferns and Rossinver, a detail that suggests the Leitrim community maintained a strong sense of its founding connection long after the saint had moved on. Erenachs, hereditary lay custodians of church land, are recorded at the site into the 15th century, pointing to an unbroken institutional presence across roughly nine hundred years. The standing fabric of the church is built of uncoursed mortared sandstone, with walls around 0.9 metres thick and surviving to a height of five metres at the east end. The original building measured approximately 14 metres by 8.6 metres, though the nave was later shortened by the insertion of a western wall, leaving a blocked doorway as the only evidence of the earlier arrangement. A modified two-light lancet window survives in the eastern embrasure.

Among the most interesting objects on the site are three carved stones. One sandstone slab carries an incised cross with expanded terminals; a second, tapering slab bears a circular cross-head rendered in false relief with a double-incised shaft; and a third stone, distinguished by two cupmarks, has been reused as an ordinary headstone. Cross-slabs of this kind are early medieval grave markers, sometimes pre-Norman in date, and their presence here alongside the well and the long documentary record gives the site a density that its quiet, low-lying setting does little to advertise.