The belief among historians that the ship containing the 20 and odd had come from the West Indies had been debunked not too long ago by a historian doing research in the Spanish Archives. Here is a link to the article. It shows that the Africans from the "White Lion"(Which was the name of the ship operated by Captain Jope which landed in Virginia in 1619) were likely from Angola.

http://archive.southcoasttoday.com/daily/09-06/09-04-06/15world-nation.htm