That's basically about all you can get regarding N/A ancestry. The "Rolls" were actually a Census done by the government to keep track of Native Americans--separate from the whites. Many tribal people avoided any contact with government officials, so this "census" could hardly be accurate. Neither for sure could the information given was true, either.
The other way you can prove ancestry is a DNA test, but don't expect that to be accurate either. For one thing, they are not emphasizing that DNA test can only trace the MALE Y chromosome to get the paternal line. That means you have to be a male to trace the paternal side. If you suspect your male side was N/A you need a male relative to submit a sample.
. When white man first came to this country in the early years, there weren't many single WHITE women. N/A women could be traded, bought, and sold. It's the reason why I have Cherokee blood. One of my family names is in the Cherokee Rolls.