Members of the Fiennes family, descended from the Norman counts of Boulogne, had distinguished themselves in the reign of Edward I, whose second queen, Margaret of France, was their kinswoman. However, during the wars begun by Edward III their loyalties were split: the main branch of the family espoused the cause of the French king and those who supported King Edward witnessed the loss of their own substantial interests in France. In compensation, through a succession of lucrative marriages, notably to the heiresses of Filoll, Forester and Monceux, the Fiennes had come into possession of widespread estates in England. These included Ascot and Lyneham (Oxfordshire), the bailiwick of ‘Twicchene’ in Windsor forest, and Wolley in White Waltham (Berkshire), ‘Asshall’ in High Ongar (Essex), Compton (Hampshire) and Burham and Cudham (Kent). Most important was the property at Herstmonceux, worth as much as £40 a year even in 1375, when the land was for the most part waterlogged. Roger was 17 when he inherited the family estates following his father’s death in 1402. He was made a royal ward, and the influential King’s knight, (Sir) John Pelham, constable of the nearby castle of Pevensey, paid the Crown 200 marks for his marriage.
When Roger’s maternal grandmother died early in 1407 he added substantially to his holdings in the same area of east Sussex, notably with a second manor at Herstmonceux and property at Wartling adjacent to the Fiennes manor of ‘Old Court’. He had delayed making formal proof of age, but now did so in order to take possession of his father’s and grandmother’s legacies.
In 1411 Fiennes placed his estates in the hands of a distinguished group of feoffees, headed by his former guardian Pelham, and including his kinsman, Sir Thomas Clinton, and the Derbyshire landowner, Sir Thomas Gresley. It was they who two years later were to apply for a royal licence to block off a road passing through Herstmonceux park, thus inaugurating the extensive building works which were to mark Roger’s ownership of Herstmonceux. His estates in Sussex were in the possession of these feoffees in 1412, when they were valued for the purposes of taxation at £100 a year. In the same assessments, his Hampshire lands were worth 20 marks p.a., and his Kentish holdings £52 p.a. Given that he also held manors in three other counties, as well as his share of the Say inheritance, it is clear that Fiennes could expect an annual income well in excess of the £165 here recorded.
In 1412 Fiennes was most likely overseas in the duke of Clarence’s company; and his spurs were won before the end of the year. He provided seven men-at-arms and 24 archers for Henry V’s invasion of France three years later, there proving his worth as a soldier by taking a number of prisoners on the field at Agincourt. His acceptance into the ranks of ‘King’s knights’ may well have antedated his first return to Parliament in March 1416, although it was not until the following November that he received a generous retaining fee of £40 a year, half of which was to be derived from the fee farm of Cambridge and the remainder from the wool customs collected at Southampton. Emerging as a war-captain of some prominence, Sir Roger was contracted for the King’s second expedition to France in 1417 to supply nine lances and 30 archers, thereafter serving throughout the conquest of Normandy, including at the sieges of Louviers and Rouen. Following the fall of the Norman capital in January 1419, he was empowered to accept the surrender of Caudebec in Henry V’s name, awarded the posts of bailli of Caux and captain of Longueville, and, like other leaders, was granted a stake in the duchy in the form of a landed estate to hold in tail-male. He seems to have remained in France throughout 1419 and 1420, returning home with the King in February 1421. In April following, King Henry awarded him custody for life of Portchester castle, commanding the entrance to Portsmouth harbour. Having once more entrusted his estates to feoffees, Fiennes followed the King back across the Channel in June, and within a month he was serving in the Bastille at Paris. He was not to see England again until after Henry V’s death.
Henry VI’s council confirmed Sir Roger’s annuities and his keepership of Portchester. At one point he was considered as a suitable candidate for the post of mayor of Bordeaux, but for the time being he stayed at home, acting for most of 1423 as sheriff of Surrey and Sussex. Then, in March 1425, he agreed to recruit 30 men-at-arms and go archers for service in France under the Regent, John, duke of Bedford, and to take command of the other forces which were to cross over to join the duke in June. He returned to England after six months. It was during his second Parliament that, in February 1430, Fiennes contracted to join the large entourage of the young King for his coronation as king of France. Once again he entrusted his estates to the care of friends, in whose keeping he also left his moveable goods. This, beginning an absence of two years, was probably his final journey overseas.
In 1434 Fiennes was listed among the gentry of Sussex who took the oath not to maintain those who broke the peace. He had already begun to put the substantial profits of his military exploits to use for the further aggrandizement of his family in south-east England, namely by purchasing in conjunction with his brother, James, two manors at Hever in Kent, as well as other property in Surrey. To a certain extent Sir Roger now usurped the place once held in Sussex by Sir John Pelham. A year after Pelham’s death in 1429 he had obtained from his illegitimate son a release from suit of court, castle guard and all other services owed to the honour of Hastings, and confirmation of this privilege was received subsequently from one of Pelham’s heirs and from Sir Thomas Hoo after his acquisition of the honour. Fiennes also secured from the Pelhams the hundred of Foxearle.
There is no evidence to suggest that Sir Roger was ever so closely attached to William de la Pole, marquess of Suffolk, as were his brother, Sir James, and his own two sons. Sir James’s rapid emergence as second only to Suffolk as the most influential and detested of the King’s lay advisors occurred soon after his brother’s retirement from Court, that is, when, in February 1447, he took the place of the duke of Gloucester (in whose death he was suspected of complicity) as constable of Dover and warden of the Cinque Ports. Created Lord Say and Sele at the close of the Parliament of that year, James rose to be treasurer of the Exchequer in September 1449.