The Gesta Danorum (book 2), by Saxo Grammaticus, contains roughly the same information as Beowulf, the Chronicon Lethrense and the Annales Lundenses: that is, that Ro was the son of Haldanus and the brother of Helgo, and the uncle of his successor Roluo Krage (Hroðulf). It is only said about Ro that he was "short and spare", that he founded the town of Roskilde, and that when their father Haldanus died of old age, he shared the rule of the kingdom with his brother Helgo, Ro taking the land and Helgo the water.
Ro could not defend his kingdom against the Swedish king Hothbrodd, who was not happy with warring in the East but wished to test his strength against the Danes (Oliver Elton's translation):
|“||Fain to extend his empire, he warred upon the East, and after a huge massacre of many peoples begat two sons, Athisl and Hother, and appointed as their tutor a certain Gewar, who was bound to him by great services. Not content with conquering the East, he assailed Denmark, challenged its king, Ro, in three battles, and slew him.||”|
Ro was, however, avenged by his brother Helgo, who then promptly went east and died in shame (because he discovered that he had fathered Roluo Krake with his own daughter Urse.) Roluo succeeded his father and uncle to the Danish throne.
The Gesta Danorum also agrees with Beowulf in presenting Hrothgar (Ro) and Halga (Helgo) as brothers and the sons of Healfdene (Haldanus). Moroever, like the Chronicon Lethrense and the Annales Lundenses, it presents Hroðulf (Roluo) as the son of Halga and his own daughter. A striking difference is that the Swedish king Eadgils (Athisl) is pushed forward a generation, and instead Saxo introduces Hrothgar's killer Hothbrodd as the father of Eadgils, a place that other sources give to Ohthere. A similar piece of information is also found in the Chronicon Lethrense and the Annales Lundenses, where Halga had to kill a man named Hodbrod to win all of Denmark. However, Saxo also adds the god Höðr as the brother of Eadgils in order to present a euhemerized version of the Baldr myth, later.
The tradition of the feud with the Heaðobards Ingeld and Froda appears twice in the Gesta Danorum. The first time it tells of the feud is Book 2, where Ingeld (called Ingild) appears with the son Agnar. In this version, Ingeld's son was about to marry Hroðulf's sister Rute, but a fight broke out and Agnar died in a duel with Bödvar Bjarki (called Biarco).
The second time it tells of Froda and Ingeld is in Book 7, but here Hrothgar is replaced by a Harald and Halga by a Haldanus. It is the Scandinavian version of the feud, similar to the one told in the Skjöldunga saga, Bjarkarímur and Hrólfr Kraki's saga, where the Heaðobards are forgotten and the feud with Froda and Ingeld has become a family feud. The main plot is that Ingeld had the sons Frodo (Froda) and Harald (corresponds to Healfdene). The relationship between Ingeld and Froda was thus reversed, a reversal also found in the Skjöldunga saga and in the Bjarkarímur. Froda killed his brother and tried to get rid of his nephews Harald (corresponds to Hrothgar) and Haldanus (corresponds to Halga). After some adventures, the two brothers burnt their uncle to death inside his house and avenged their father.