At some time before 1526 Amadas was appointed one of the deputies to the Master of the Mint, william Blount, 4th Baron Mountjoy. In 1526 the coinage was altered, and a new contract was entered into between Mountjoy and his two deputies, Robert Amadas and Ralph Rowlett, and Amadas' deputy, Martin Bowes. Shortly thereafter allegations were made of wrongdoing in the administration of the Mint, and in June 1527 a commission of inquiry was set up. The commission reported in February 1528, and was highly critical of Amadas and Rowlett. In 1530 Lord Mountjoy, disturbed by the declining revenues from the Mint, and suspecting corruption, instituted a lawsuit in the High Court of Chancery against his two deputies. Unfortunately the outcome of the lawsuit is unknown; however in December 1530 Mountjoy appointed a new deputy for the Mint, the London goldsmith Hugh Welshe or Walshe, who had been one of the members of the commission which had earlier been critical of the work of Amadas and Rowlett.

Amadas refused election as Sheriff of London in 1531. He made his will on 3 July 1531, requesting burial in his parish church of St Mary Woolnoth, and appointing his wife, Elizabeth, as his sole executrix, and Thomas Howard, 3rd Duke of Norfolk, Sir Thomas More, and Richard Rich as overseers. He bequeathed the King a gold cup of £100 value. Among his other bequests was £5 to John Freeman, who had been apprenticed to him in 1507 and admitted to the livery in 1528. The will was proved 28 November 1533. His stock was inventoried after his death, and put up for sale.

After Amadas' death, his widow, Elizabeth, married, on 28 August 1532, as his second wife, the Lawyer and Speaker of the House of Commons, Sir Thomas Neville, (d. 29 May 1542), fifth son of George Neville, 2nd Baron Bergavenny (1436–1492), by his first wife Margaret, daughter of Hugh Fenn. Neville had earlier been married to Katherine (née Dacre), widow of George, 8th Baron FitzHugh (d. 28 January 1513), and daughter of Humphrey Dacre, 1st Baron Dacre of Gilsland, by whom he had an only child, Margaret Neville, who on 1 May 1536 married Sir Robert Southwell. Elizabeth predeceased her second husband.

In July 1533, an Elizabeth Amadas claimed that she had earlier been solicited to become Henry VIII's mistress. She predicted that Anne Boleyn would be burned as a harlot, and said that men should not be able to set aside their wives, as the King was attempting to do with Catherine of Aragon. Elizabeth Amadas claimed that her own husband had left her. She was arrested for her treasonous comments, and it is said that Robert Amadas was ordered to pay several hundred pounds for 'missing plate' owned by the King.