(Rosh) Rabbi Asher ben Yehiel

The Rosh was a major Ashkenazi rabbi who later moved to Spain. He combined the learning traditions of Ashkenaz with the legal culture of Sepharad. His rulings became extremely influential, especially because his son, the Tur, later used his teachings as a foundation for Jewish law.

For your timeline, the Rosh is important because he connects Ashkenazi and Sephardic traditions. He helped transfer German-French Talmudic scholarship into Spain and shaped the halakhic world that later produced the Shulchan Aruch.