There's a lot of possibilities to obtain different scrolls such as
scrolls from bosses on the map;
scrolls in tavern for reishi;
scrolls from alliance campaign;
reward for achievements;
drop from the soul talisman box;
and as was said - from fortune event.
Best way to level your partners is the gold reishi epic exp scrolls, but i higly disscourage you to use your golden reishi on Epic Exp Scrolls, unless you need to level up a crucial partner, like i had to get Komamura to 70 for him to be able to equip my Sado's gear.