Roger I, Encyclopædia Britannica: "Roger went to Italy in 1057 to aid his brother Robert Guiscard in his conquest of Calabria from the Byzantines (1060). They began the conquest of Sicily from various Muslim rulers in 1061 with the capture of Messina, and they completed it in 1091. The turning point of the struggle was the capture of Palermo in 1072, when Robert invested Roger as his vassal with the county of Sicily and Calabria with a limited right to govern and to tax."
