The life and influence of Rabbi Asher ben Yechiel, known by the acronym "Rosh", straddled the two great spheres of the Jewish diaspora of his time, the Ashkenazic (Franco-German) and the Sephardic (Spanish-Mediterranean) communities. Born approximately 1250 in Western Germany, Rabbi Asher studied under the famed Tosaphist Rabbi Meir of Rothenburg, fathered eight sons, and authored one of the earliest codifications of Jewish law. In mid-life he fled the persecutions of medieval Christian Europe, settling in Spain where Jews prospered materially and Jewish learning flourished in the Spanish Golden Age.

Though a penniless exile and newcomer, Rabbi Asher's genius and erudition quickly earned him a position of prestige and influence. In 1304 he was invited to to serve as the spiritual leader of the Jews of Toledo, where he established a Talmudic academy and transplanted the Ashkenazic Tosaphists' system of Talmudic interpretation and analysis. He also introduced the traditionalism and piety of the early Ashkenazic "Chassidim" (reversing the secularist trends in certain segments of Sephardic Jewry).

Rabbi Asher passed away in Toledo on Cheshvan 9 of the year 5088 from creation (1327 of the Common Era).