I've seen plenty of 'em over the years; if it was opened long enough for someone to see the edge, then yep, it's all edge-fogged. The only thing that varies is how far in (from the edge) the fog goes in. Generally it's relatively slight, but will almost certainly prevent use as 8" paper. Additionally, the outer wraps of paper will be fogged. It could be as much as 10 to 20 ft of the outer wrap (depending on size of roll).
Hopefully your first test will show it to be unfogged.