In academia, many of his scholarly works focused on contemporary Nigerian history and foreign relations.
[1] Olusanya attended Methodist Boys' High School, Lagos and studied history at the University College, Ibadan (now University of Ibadan).
[2] After completing his studies, he took up a teaching appointment in the Northern Nigerian region at Ahmadu Bello University, where his former history teacher, Abdullahi Smith was developing ABU's history department.
However, political and ethnic conflict preceding the Nigerian civil war precipitated his movement to University of Lagos in 1966.
[3] In 1984, he was appointed director-general of Nigeria's foremost foreign relations think tank, the Nigerian Institute of International Affairs.