Roger may well have been the son of Richard Juyl, a prosperous tin merchant who represented Bodmin in the Parliaments of 1371 and 1381 and served as mayor of the same borough in 1370. Richard was a tenant on the duchy of Cornwall manor of Trematon, and owned a house in Dartmouth, Devon, as well as land in Landulph, Cornwall, and property in Bodmin.
Nothing is recorded about Juyl until the year of his marriage (1376) when he was already serving as controller of the stannaries in Devon, an office for which he was accountable to the receiver of the duchy of Cornwall. His rise within the duchy administration was unusually rapid, for only a few months later he was himself appointed as receiver (apparently owing his promotion to the advisors of the young duke, Prince Richard) and he retained the post after Richard’s accession to the throne. During his receivership Juyl was named on various royal commissions in Cornwall and elsewhere in the West Country, and in August 1378 he was sent a mandate to see to the fortification of Trematon castle in view of threatened invasion from France. In the following April he made a personal loan of £20 (his entire annual salary) to the King, to help finance the country’s defence. But there were criticisms of his behaviour as receiver: in May 1379 certain Genoese merchants who had left 12 bales of spices and other wares in his keeping at Fowey complained that he had retained five of the bales for his own use. The receivership entailed the handling of very large sums of money, and even though there is evidence that Juyl spared no effort in pursuing the duchy’s debtors, he clearly found difficulty in the collection and correct disbursement of the revenues. On 17 Aug. 1381 Sir John Kentwood, the steward of the duchy, was ordered to bring him before the King’s Council to answer for certain sums of money for which he had failed to render full account, and also to confiscate his chattels and keep them until further notice. Nor were these empty threats: a few weeks later, Juyl was actually dismissed from his office and told to deliver to William Brantingham all the rentals, memoranda and account rolls pertaining to the receivership. At the same time he had to face charges brought in the King’s bench by William, earl of Salisbury, for neglecting to keep up the payments of the annuity of 200 marks to which the earl was entitled from the profits of the stampage of tin in Cornwall. By 3 Oct. Juyl had still failed to present himself before the Council, but when he eventually did so his line of defence must have been sound, for on the 25th he was appointed as escheator of Devon and Cornwall. Nevertheless, on this occasion the Council was taking no chances that he might defraud the Crown: he was required to find mainpernors for his good and faithful demeanour towards the King, along with guarantees that he would dutifully answer at the Exchequer for the profits of his new office. Accordingly he asked three highly distinguished figures, Sir Robert Tresilian, c.j.KB, Sir Peter Courtenay and Sir John Cary, to provide securities under a penalty of £100 on his behalf. Juyl’s reappointment as escheator two years later in 1383 is some indication that in this office at least he had performed satisfactorily; and, in fact, it was not until after the political upheavals of 1388 that any action was taken against him for the recovery of nearly £180 outstanding at the end of his duchy receivership. In 1389 certain of his lands and those of his mainpernors, worth £15 15s. a year, were in the hands of the sheriff of Cornwall.
The confiscation of Juyl’s property and chattels at this time followed only after Chief Justice Tresilian’s execution, and it seems clear that the two men had been business associates. Indeed, it was subsequently discovered that certain premises in Bodmin (notably a house known as ‘Gromond’, a park, meadows and ‘Fattestenements’) had been illegally acquired by Juyl and transferred to Tresilian.