Sir Roger Mostyn (1567 18 August 1642) was an English politician who sat in the House of Commons from 1621 to 1622.Mostyn was the eldest surviving son of Sir Thomas Mostyn of Mostyn. His father was MP for Flintshire in 1577. He matriculated at Brasenose College, Oxford on 8 May 1584 aged 16, and was admitted at Lincoln's Inn in 1588. In 1602 purchased a 13 year lease of Mostyn Colliery for Pds. 70 and immediately began a programme of expansion. He was knighted on 23 May 1606. By 1616 he had three pits on the colliery site and by 1619 the colliery was worth in the region of Pds. 700 annually to the Mostyn family, which suggests a fairly substantial output.In 1621, Mostyn was elected Member of Parliament for Flintshire.Mostyn died at the age of 75 and was buried at Whiteford.Mostyn was the grandfather of Sir Roger Mostyn, 1st Baronet.