Rock wool insulation was a substitute for asbestos insulation. You bought one or the other, not both.
It is possible that a brand of Johns Manville Spintex rock wool insulation from the 1950s may contain asbestos. Asbestos was commonly used in insulation materials during that time period. To confirm if the specific product contains asbestos, it would be best to have it tested by a certified laboratory.
Accra is the capital city of Ghana.