Roche was involved in insurance scams, insuring ships then intentionally wrecking them, occasionally using the alias John Eustace. In November 1721 Roche and three associates booked passage on a French vessel sailing to Nantes. Roche was charismatic and had knowledge of seafaring, and convinced the ship’s master to let him handle the vessel. At a signal they rose up, slaughtered the French crew, and threw the captain overboard. They debated where to sail next, including Newfoundland. Afraid of being discovered, they modified the ship’s appearance, altered the ship’s logbooks, and renamed it Mary before sailing to Rotterdam to sell its cargo.
Roche was eventually found in London and imprisoned in Newgate. Tried for piracy, he was found guilty and hung in August 1723. The public was disappointed at the execution: Roche "was so ill at the time that he could not make any public declaration of his abhorrence of the crime for which he suffered."
