Excerpts from Books and Wikipedia
Roncesvalles's fame is due to the Song of Roland, a heroic epic poem from circa 1100 celebrating count Roland's heroism in the battle. The author, Turoldus, gave the battle a makeover, turning Charlemagne's Spanish campaign into a prototype crusade." [1001 Days]
"Stories were told about the minor ambush until it had been transformed into a pivotal battle; Roland became the hero of the first French epic, the twelfth-century Song of Roland, which turns the bloody incident into a major conspiracy between the Arabs of Zaragoza and a traitor within Charlemagne's own camp. . . But in reality, the Battle of Roncesvalles ended Charlemagne's ambitions in al-Andalus. He never pushed his way past the Pyrenees again." [Bauer: Medieval World, p. 378]