The commentary on the Talmud authored by the Rosh, Rabbi Asher ben Yechiel, is found in the back of nearly every edition of the Babylonian Talmud. The popularity of his commentary reflect his clarity of thought and expression, and his halachic authority as the close disciple of the Maharam, Rabbi Meir of Rothenberg (1215-1293). The Maharam was the last of the German Baalei Tosafos. Thus, his student, Rabbi Asher ben Yechiel, assimilated and represented the Ashkenazic tradition of Torah learning.
Because of the savage activities of the Crusaders, Rabbi Asher fled to Spain in 1306. His first stop was Barcelona, where the Rashba gave him a cordial welcome. He then moved on to Toledo, where he became Chief “Dayan,” Judge in matters of Jewish Law, and Chief Rabbi of the community.
The Rosh was not pleased by the Spanish approach to Torah learning, which he saw as attributing excessive value to philosophy and other secular studies. He felt that the unavoidable consequence of the Spanish approach would be the “watering down” of the focus on the Talmud, the true source and repository of Jewish wisdom. Yet, by the sheer greatness of his Torah ideas, the influence of Ashkenaz began to penetrate the Spanish Torah world.
The halachic opinions of the Rosh were binding upon Ashkenazic Jewry. But Spanish Jewry also began to take into account his opinions in their formulation of Jewish Law. Rabbi Yoseph Karo (1488-1575) in the “Bais Yoseph” and in the “Shulchan Aruch,” classics of Jewish Law, gave equal weight to the halachic opinions of the Rosh as to the opinions of the Sephardic Torah giants the Rif and the Rambam. His method in those cases where the opinions of Ashkenaz and Sepharad differed, was to decide the Law by “taking a vote,” as it were, among those three opinions, and the Law would be in accordance with two out of the three opinions.