After few decades, in 1656, the Donamon Castle was bought by one of the henchmen of Cromwell, Robert King of Rickingham. Later on, in 1668 the castle was leased to Thomas Caulifield by Lord Kingston, who was son of the King. The castle was once under the control of an IRA unit led by Seán McCool and Mick Price, with the aim to establish a training camp. Centuries later, precisely in the year 1939, the castle was bought by the Divine Word Missionaries from Germany. At that point in time, the Donamon Castle was in a ruinous condition and even the garden a wilderness.
Years later, OCA conducted a comprehensive survey and prepared detailed drawings of the existing structures of this 14th century fortified residence. Thereafter, Mary O’Carroll was assigned the task of refurbishing the castle as well the 19th century extensions. With renovation, everything was restored to render grandeur to the Donamon Castle. At present, the Donamon Castle that overlooks River Suck is a popular historical landmark of Roscommon that attracts tourists year-round.