I payed attention alot in my history courses in HS and college when we came to discuss Rome and funny thing is Rome took various peoples of many backgrounds (white, black, asian) and still lasted around 1000 years I can guess why, all learned and assimilated into the Roman culture and the Roman way.
Who specifically was “Asian” and “Black” that you referred to as being assimilated by Rome?
If you refer to Syrians and Eastern Greeks as Asians, that’s a bit of a stretch.
All areas of Africa ruled by Rome weren’t inhabited by Sub-Saharan Africans. Unless you’re counting the short-lived province of Ethiopia?