Roughan Castle was built in c. 1618 by Andrew Stewart, eldest son of Andrew Stewart the third Lord Ochiltree, Lord Castlestewart who came from Scotland during the plantation and established the nearby town of Stewartstown. Thus, Stewart junior acquired the land of Ballokevan from Robert Stewart between 1610 and 1619 and here he built his castle overlooking the lough.
A small square castle, Roughan stands three storeys high encompassing a central tower 20 feet square, flanked by thick rounded towers at each corner measuring 8 feet in diameter and which convert to square rooms in the upper floors. This castle incorporates aspects of Scottish corbelling and on the south side above the second floor an arch with moulded corbels connects the corner tower. The exterior walls have a moulding string course which divide each floor.
The windows of Roughan Castle are rectangular, slightly arched inside in the thickness of the wall, and the cut stone frames which were partially damaged have now been restored. Entrance to the castle was gained by a door in the north-west tower which was initially round headed. Immediately inside a spiral staircase ascended above the door, and the main floor was of timber floorboards. Constructed with defensive objectives playing an important factor, an underground passage ran below the castle and the ground floor of each of the towers have several gun loops.
There are open fireplaces in the first and second floors on the north wall, and as the fireplace on the first floor is larger, and the inner walls of the ground floor are less carefully finished than higher, we may assume that the main living quarters for the family were on the first floor. There is a small head carved in very flat relief on a stone under the second floor doorway leading into the south-eastern tower.
A crannog – an artificial island – is located on the nearby lough, which Roughan Castle overlooks. A number of plantation castles have been built near to crannogs, suggesting that areas such as the region around Roughan Castle were already areas of established settlement. Crannogs were utilised during the early Christian Period – 6th to 8th century – and were distinguished as a site of high status. Thus, a degree of continuity may be suggested at Roughan with one lord merely being replaced with another. Hence, while Andrew Stewart may have commissioned the building of Roughan Castle, it is feasible that an estate with a number of tenants had already existed here prior to the plantation.
Upon the death of Andrew Stewart, Roughan Castle and estate was acquired by his brother John, and later transferred to the youngest of the brothers, Robert Stewart. When the 1641 Rising took place Robert Stewart became entangled. Hence, it appears that having had close connections to the O’Neills – it is believed that Stewart’s first wife was Catherine O’Neill, granddaughter to Hugh, last Earl of Tyrone – Stewart was appointed an officer in the rebel forces, by Phelim O’Neill leader of the rebellion. However, Robert Stewart was not questioned about his part in the rebellion until twelve years later, and by such times he had become a loyal servant of parliament and was exonerated from having played any part in the rebellion. Later the castle also belonged to Sir Phelim O’Neill, executed for his rebellion of 1653.