Roger Kirkby of Kirkby Ireleth (c.1649-1709) was MP for Lancaster 1685-7 and 1689-1702. He was a Preston out burgess at the 1662 and 1682 guilds and high sheriff of Lancashire from 1708 until his death. Kirkby was a career soldier, listed as a captain in a foot regiment in 1685 and as a colonel by 1693, at which time he had been appointed as governor of Chester. In politics he was a Whig, a loyal supporter of Lord Brandon, leader of that party in Lancashire. 
He is probably the ‘Capt Kirby’ who makes several appearances in the Bellingham/Rawstorne diaries, where there are occasional references to a Mr Kirkby. This could be Roger, or possibly his uncle William; a William Kirkby was in Preston with Lawrence Rawstorne on 21 February 1685 and a Col Kirby and his uncle were in the town 21 June 1689. On 25 July 1689 a Col Kirby was in Preston: this could be Roger, by then possibly promoted colonel. The same man appears in both Rawstorne’s and Thomas Bellingham‘s diaries for 14 August 1689, but whereas Rawstorne names him colonel, Bellingham has him as ‘Mr Kirkby’. The Brandon connection is brought out 15 June 1689 when Bellingham writes from Preston, ‘Here came ye Ld Brandon, Gerard [probably Brandon’s son], and Capt Kirby, in order to rayse ye militia of ye whole county’.