Joseph,
The Rosh HaYeshiva was the head of the Yeshiva, R’ Shmuel Belkin. Rabbi Solovetchik was the Rosh Yeshiva, along with R’ Lifshitz, R’ Alpert, R’ Zaks etc. Like a magid shuir in the Mir is a RoshYeshiva but not the head like R’ Noson Tzvi Finkel.