Hróa þáttr heimska or the Tale of Roi the Fool is a short story (þáttr) from Iceland about a Dane called Hrói the Fool who is helped in a legal dispute by the wise old Swede Þorgnýr the Lawspeaker, and which takes place in the late 10th century. It is preserved in two versions of which one (HróFlat) is found in Flatey Book (GKS 1005 fol 344-348, ca 1387-1395) and the second one (Hró AM 557 4°) in the Arnamagnæan Codex (AM 557 4° 41r-42v, ca 1420-1450) in Copenhagen.
In the version of Heimskringla which is found in the Flatey Book, it is inserted together with Styrbjarnar þáttr Svíakappa in the description of Olaf Haraldsson's wooing of the Swedish princess Ingegerd Olofsdotter. Their purpose appears to be to present the Swedish court, its traditions and Þorgnýr the Lawspeaker.
He had one blue eye and one black eye, and he was a skilled smith and trader. However, each time his trade had made him wealthy, he went to sea and lost it all. The third time, he went to king Sweyn and asked him to be his business partner. The king consented although his court advised him not to deal with such an unlucky man as Hrói.
However, the king's good luck prevailed over Hrói's back luck and Hrói became a wealthy man, and one day he shared the wealth with the king and finished their partnership, against the king's wishes who'd rather he stay at the court and marry.
Then he went to Sweden and struck a deal with Helgi a red-haired courtier of king Eric the Victorious. However, after the deal had been made and the goods delivered, Hrói came to fetch the merchandise, and discovered that Helgi had tricked him. Helgi said that he had delivered the goods, but Hrói had not been there to fetch them and so Helgi had taken them back. Helgi also stated that Hrói had broken the king's law by not guarding his goods, so that a thief might steal them.