Sir Nicholas Maltbie, to whom the castle was leased in 1577, asked to be made Seneschal of Roscommon in 1580 as compensation for rebuilding the fortress.
Captain Brabazon, Governor of Connaught, summoned a meeting of the chiefs in the castle in 1582. It was held in the “Tower of the Narrow Passages,” and the joistings giving way the whole meeting, including the Governor, was precipitated to the bottom. Chief O’Flanagan died from the fall.
After this the English constable was murdered, and Sir Henry Sydney left a garrison in the castle.
Sir Nicholas Malbie died in 1584, and the castle remained in his family’s possession for some years afterwards. In 1609 Lady Sydley, widow of Henry Malby, Esq., asked allowance for the repairs of the castles of Roscommon and Longford, both of which she rented from the Crown. Roscommon had been ruined by various garrisons which had been placed there by Sir John Norris and others.
One of the charges against the northern Earls was their intention to seize Roscommon Castle amongst others.
The garrison made a brave defence against the Irish in 1642. The castle was chiefly defended by Scotch warders. It is quaintly noted that at the beginning of these “commotions” it had belonged to Lord Grandesson.
Three years later General Preston arrived and laid siege to it, opening fire on both town and castle.
On the ninth day of the siege the garrison offered to make honourable terms, which were accepted. The same day the besieging party had a sharp encounter with a relieving force, who were, however, defeated, and the castle surrendered. Captain Leicester was left in command.
It remained in the possession of the Irish forces until 1652, when it was delivered on articles to Commissary-General Reynolds, of the Parliamentary troops, by Captain Daly.
It is probable that it was demolished at this time. Tradition states it was burned by fugitive Irish after the battle of Aughrim, and some blackened joists are pointed out in corroboration.