Fredegar relates (Chronicle, 71) that at the beginning of his reign he put to death many insubordinate nobles, and that in his efforts for peace he maintained very strict discipline.

[1] Rothari conquered Genoa in 641 and all remaining Eastern Roman territories in the lower valley of the Po, including Oderzo (Opitergium) in 641.

Before commencing a campaign the rest of Eastern Roman Liguria in 643, he issued the Edictum Rothari a compilation of Lombard law based on ancient customs.

The exarch of Ravenna, Plato, tried to regain some territory, but his invading army was defeated by Rothari on the banks of the Scultenna (the Panaro) near Modena, with the loss of 8,000 men, in 645.

A baptistery in Monte Sant'Angelo is traditionally known as the "Tomb of Rothari", although he was probably buried in the church of San Giovanni Domnarum in Pavia, founded by his wife Gundeberga.