I wouldn't call it tons, flah, but you gave great examples. Of course, living color (who is freakin' awesome still . . . check out vernon reid's solo stuff!) is the king of that list. Bad Brains is very influential too in some circles, but definitely less known.
Overall, the number of black performers who crossover to rock/heavy rock is very very small. Nowadays it would be pointless and unprofitable, as rock is, at the time, commercially dead. But even in the heyday of rock, there were proportionally few black performers that crossed over into hard rock or heavy metal. Jimi hendrix, living color and others are quite remarkable, but numbers-wise not a large group of people.
I don't know why. I've always found it curious too. If you listen to Grant Green's funkier work, etc, miles davis on bitches brew, etc, you can see that all the technical elements for jazz fusion, then straight-on heavy music are all there. They just don't do it.