In Rohan, the Felix box can be found inside Black Dragon Sanctuary. This is the most difficult part because there are lots of monsters inside the sanctuary and this is not exactly your Rohan race territory. So when you are about to open the box, you'd better party up with a friend and just leave the party. Go inside the sanctuary and head straight then take two right path whenever you see a split path. After the two split paths, head forward and you will a room with flame spites and monsters.
You need to open the Felix box to accomplish the third part of Scout Job Change Quest. Then return to Senecca to receive the fourth part of the quest. Getting 15 items(Rohan Crone) by killing 15 Morvol monsters which Teleport to Pine Plateau Bindstone, go west to Shrouded Mansion then continue going to west from there until you find Morvols is also needed.
After you kill 15 of the monsters, go back to Kai'non, you will find that you are almost finished in the Rohan Scout Job Change Quest. Then talk to Zhonat Rotus for your last quest to become a Rohan Scout. Congratulations, you will be a Rohan Scout just need to speak with Senecca. Just have a try with Rohan powerleveling.