No the populations of North Africa were already established similar to the present day well before Roman control. Phoenicians and later Carthaginians had established large cities and trade networks. Berbers and other groups had been present in the region for thousands of years. Romans werent present in the area in large enough numbers to impact the genetics of the peoples. Small garrisons and a few veterans establishing farms was all there was

In most cases North Africans were never black skinned. In fact in the present day dark skinned North African peoples are largely the result of the Arab slave trade transplanting Sub-Saharan Africans.