Charles Homer Haskins wrote about the Normans in Sicily as elegantly and insightfully as anyone before or since. In The Normans in European History he expressed his admiration for King Roger II (1130–54):

Haskins may have admired Emperor Frederick II even more but argued that many of Frederick's virtues had their origins in Roger's cosmopolitan Palermo. ‘Nowhere else’, he observed, ‘did Latin, Greek, and Arabic civilization live side by side in peace and toleration.’ He pointed out that Sicily was the ‘natural meeting-point of Greek, Arabic, and Latin civilization, and a natural avenue for the transmission of eastern art and learning to the West’.

The scattered artifacts and architectural monuments that remain of Roger's capital city, Palermo, provide startling and evocative evidence for Haskins's generalization. Art historians have demonstrated that Roger exploited all three cultures in his kingdom. He imported objects, craftsmen and materials from all over the Mediterranean to build and decorate his buildings. These multicultural artisans also provided him with his robes, the symbols of his office, and even his tombs. Historians have long known that Roger adopted Byzantine and Arabicpractices and utilized Greeks and Arabs in his court; he was indeed ‘a ruler between East and West’.

Roger II produced a body of legislation that scholars have dubbed the Assizes of Ariano. His legislation was important for several reasons: no other secular European prince promulgated such a sophisticated body of laws in the first half of the twelfth century; no other ruler ordered his legislation compiled into a systematically organized collection; his legislation reveals a close connection to the teaching and study of Roman law in Northern Italy; his legislation may be the earliest example that we have of the nascent Ius commune's influence on secular law; and, finally Emperor Frederick II's commission of jurists incorporated more than half of his legislation into the Constitutions of Frederick II in 1231 (also called The Liber Augustalis or The Constitutions of Melfi in the older literature), which remained the law of the land in Southern Italy until the early nineteenth century.