Robert Dillon, 2nd Earl of Roscommon PC (Ire) (died 1642) was styled Baron Dillon of Kilkenny-West from 1622 to 1641 and became earl of Roscommon only a year before his death. He supported Strafford, Lord Deputy of Ireland, who appointed him as one of the keepers of the King's seal. Lord Kilkenny-West was in December 1640 for a short while a lord justice of Ireland together with Sir William Parsons.