The country house that once stood here was already a reduced version of itself by the time the twentieth century had finished with it, and what remains today is a single projecting wing of a building that was once considerably more ambitious. An early photograph, reproduced in Grove White's survey compiled between 1905 and 1925, shows what the house looked like in something closer to its original form: a long, composed entrance front facing north, with a string course, that horizontal band of moulding used to mark the division between floors, separating the ground and first storeys. The central three bays stepped forward slightly, framing a pedimented doorway, and sash windows with their original glazing bars ran across the facade. At either end, deep projections curved outward in bowed forms, giving the whole composition a generous, well-proportioned spread typical of late-eighteenth-century Irish domestic architecture.

By the time Mark Bence-Jones catalogued it in 1978, the house had been substantially reduced, leaving only the western projection standing. That surviving wing, oriented along a north-south axis, has since been converted into a dwelling and altered further, with a hipped roof to the north and a gabled end to the south. The western elevation retains a Venetian window lighting a stairway projection, which offers a small but clear sign of the original quality of the building's interior arrangement. A three-bay, bow-ended addition was made to the north, and more recent extensions have been added to the east. The site itself appears to have a longer history beneath all of this: the Down Survey barony map of 1655 to 1656, one of the earliest systematic cartographic records of Irish land, marks a castle on or very near this location, suggesting that Rockforest was a place of some significance well before the Georgian house was ever built.