He came up in an era where heavyweights were still very relevant to the mainstream and commanded big money. Even so, he still was a very well known fighter, but didn't get the kind of checks Floyd does today.
He was definitely mainstream, I wouldnt really say cash cow. But very well known either way.To be a cash cow you have to have more than just skills(roy had plenty). Also, I think he was in the wrong weight divisions to be a cash cow.