Board Thread:Wiki Discussions/@comment-3238846-20140422105553/@comment-3279282-20140428100703

No, the databook doesn't say that Roshi mastered those natures. It says that he mastered the nature which fuses those two natures. The problem is, we don't know what "power" he borrowed from Son. Maybe Roshi did it like the Kazekage and simply copied what Son did? We don't know at all.