James was born about 1605[2] in Ireland, the eldest son of Robert Dillon and his first wife Margaret Barry.
His family was Old English and descended from Sir Henry Dillon who came to Ireland with Prince John in 1185.
[6] in a ceremony performed by the Lord Deputy Oliver St. John in the Presence Chamber of Dublin Castle on 25 January.
[8] In consequence of this advancement, Robert, the heir apparent, James's father, was styled Lord Kilkenny-West, as a courtesy title from 1622 to 1641.
[9] She was a sister of Thomas Wentworth, 1st Earl of Strafford, the formidable and (for a while), all-powerful Lord Deputy of Ireland.
[16] In its first session the parliament unanimously voted for four subsidies of £45,000[17] to raise an Irish army of 9,000[18] for use by the king against the Scots in the Bishops' Wars.
[19][20] On 3 April 1640, Strafford (i.e. Wentworth) left Ireland,[21] called to England by the king to help him manage the Bishops war against the Scots.
[40] Roscommon returned to Ireland with Ormond sailing on a man-of-war sent by William II, Prince of Orange to Le Havre to carry them to Cork where they arrived on 29 September 1648.
[41] He died at Limerick in October 1649, at the house of the Anglican Bishop Bramhall, of an accidental fall down a flight of stairs.
[42] According to legend, his son, then in exile at Caen, knew of his death at the moment it happened, although the official news did not reach him until two weeks later.