The spread measures roughly ten metres in length and fourteen metres in width, and immediately to its south there appears to be a spring. That proximity is not coincidental.

A fulacht fia is, in its simplest form, a cooking place. The typical arrangement involves a trough, usually lined with wood or stone, into which water was poured and heated by dropping fire-cracked stones from a nearby hearth. The shattered, blackened stones were then raked out and piled to the sides, forming the characteristic horseshoe-shaped mound that survives at so many sites across Ireland. The presence of a water source nearby was essential to the process, which is why fulachtaí fia so often appear beside streams, springs, or marshy ground. The Rosnascalp site fits that pattern well. These monuments are generally associated with the Bronze Age, though their precise function has been debated, with some researchers suggesting uses ranging from food preparation to textile processing or bathing. The burnt spread here, substantial in area, suggests repeated and perhaps sustained use over time.