Scrolls become obsolete after a certain level, so your only options are to keep collecting them from daily exams and such or sell them at 500 coins each. I propose a conversion system that would allow players to use their old scrolls to gain the next level so to speak.
Example. Genin>Chunin>Jonin>Anbu>Kage

RNG of gaining Kage scrolls is terrible, this would alleviate that pain greatly and its not like people are beating exams 80+ easily unless they have pains, hashirama, etc.