Prior to his marriage, Rollo was known as a fearsome Viking warrior, with an impulsive streak, and wrought with internal struggles. Rollo participates in the Norsemen-Balts Battle with his younger brother Ragnar. During the battles, Rollo fights with typical Viking viciousness. The three head to a tavern where Ragnar reveals a device to his brother which would keep a journey west, over open ocean, on a true course. He demonstrates how this device works, showing it to be a sun dial. Rollo witnesses the execution of Eric Trygvasson.
Rollo and Ragnar are shocked when after his execution, Earl Haraldson curses Eric, thus making it so that he will not be able to enter Valhalla. Rollo then accompanies Ragnar on the first raid to England , despite their ruler, Earl Haraldson, refusing to allow them to go.
He makes no secret of his attraction to Lagertha , Ragnar's wife, and expresses his continuing sadness that she chose Ragnar over him. During the raid of Lindisfarne 's monastery in the Kingdom of Northumbria , Rollo walks in on Ragnar talking to a Christian named Athelstan. Rollo insists on killing him but Ragnar forbids it, declaring the monk is worth more alive than dead. Surprised, Rollo reminds his brother they are equals and attempts to kill Athelstan anyway. However, Ragnar pushes his brother back, causing Rollo to angrily chop the crucifix in the room to pieces, telling Athelstan that is how much he respects his God before storming off and leaving for the boats taking Athelstan, slaves, and treasures with them.
Unable to ignore the riches this unsanctioned journey has returned, Earl Haraldson has no choice but to agree to let these warriors undertake a second trip out. Rollo, Ragnar, and their crew land on the Northumbrian shores again.
This time they are welcomed by a few Anglo-Saxon warriors, however, Rollo doesn't trust them and suggests that they kill them, and they do just that. After the bloodshed on the beach, the Vikings choose the Sabbath to invade the town of Hexam and unleash a flood of violence and panic. Rollo spares an old, sick man, and gives him a glass of water to drink before taking the iron jug and cup. When Lagertha later kills Knut for trying to rape a Saxon woman and her, Ragnar falsely claims that he killed Knut so as to protect his wife and is put on trial by Earl Haraldson.
