He 5th Baron was Thomas de Ros, he was succeeded by his eldest son, John de Ros - 6th Baron; d: 1393/4 - was succeeded by his brother, William de Ros, - 7th Baron; d: 1st September 1414 - was succeeded by his eldest son, John - 8th Baron; d:? - was succeeded by his brother, Thomas - 9th Baron; d: 18th August 1431 - was succeeded by his eldest son, Thomas de Ros - 10th Baron; d: 4 November 1461 - his honours being forfeited, but on the accession of King Henry VII returned to his elder son, Edmund de Ros, who d: 13 October 1508, unmarried, "and the Barony fell into abeyance from 1687 for nearly a century and a quarter.called out of abeyance in 1896 in favour of Lady Henry Fitzgerald, who assumed the additional surname of de Ros and was mother of the late and present Lords de Ros"
Actually, Thomas (1336-1384) was the 4th Baron, and William (1368-1414) was the 6th. See the second edition of Cokayne's *Complete Peerage*, vol. XI, p. 95, note (h), referring to the summons of Robert (d. 1285), whom you are probably calling the first Baron, to Montfort's 1264 Parliament: "In 1616 the Barony was allowed precedence from this writ, a decision accepted by the Lords in 1806 ... ; but these writs, issued by
Simon in the King's name, are no longer regarded as valid for the creation of peerages." The Ros Barony is now dated from the summons of William de Ros (d. 1316) in 1299. He 4th Lord Ros. He lived of Helmsley, Yorkshire.