There are two families of color from the eastern shore named De Rosario and Rosario.

The progenitors are Phillip Rosario, an "indian"

and another Lawrence De Rosario, no race is described. His wife, though, is described as being a "free negro". De Rosario might have been Portuguese.

I looked up the surname. It is common in Italy and Portugal. Phillip might have been a native american from the Portuguese colonies in the new world or he could have been from Portugal. I remember reading that there was a thriving native american slave trade from the Old World to Spain and Portugal. Sometimes native americans from the carribean or south america wound up in the new world colonies.