Asher ben Yechiel (also called the Rosh) was born c. 1250 in Western Germany and died c. 1328 in Toledo, Spain. His father was his first teacher, a follower of Judah b. Samuel HeChasid. His major teacher, however, was Meir ben Baruch of Rothenberg with whom he studied in Worms.
When Meir ben Baruch was imprisoned, Asher became the leading rabbi in Germany. He worked diligently to get Meir released. He survived the Rindfleisch massacres of 1298 and decided to leave Germany in 1303. He was welcomed by Solomon b. Abraham Adret and was immediately pulled into the Maimonidean Controversy. Like Adret, he feared that philosophy would turn students away from Torah study. However, he too feared a schism and supported Adret's compromise. In 1305 he became the rabbi of Toledo.
He was rigidly honest and defended the authority of his position. When a rabbi refused to accept his position, he threatened the man with execution. He wrote a code of ethical sayings covering all aspects of daily life.
Asher ben Yechiel introduced the French/German discipline of Talmud study to Spain. He synthesized Meir ben Baruch's positions with Spanish tradition and custom. He was the acknowledged Halachic authority, and students flocked to his yeshiva. He wrote more than 1,000 responsa. He wrote commentaries on many tractates of the Talmud. His son, Jacob ben Asher, included many of his legal positions in his famous code, the Tur.
Asher ben Yechiel thus provided a personal bridge between French/German talmudic scholarship and Spanish Jewry.