Roles can be set for each individual character, and the roles character play in the party affect attributes and how they act during battle (when controlled by the game AI). There are roles that provide considerable status bonuses on top of “boosting” the character AI by employing special tactics and enhancing their “judgment”.
You can make battles much easier by setting roles that play off each other, and you may set up to four roles per character. Please note that potency of certain roles-specific factors may vary depending on the role, even if the effect is the same. That said, it's always a good idea to stick with roles complement the character's skills and stats. For example, an attacker like Fidel should be given roles that allow him to act and attack frequently, boost his ATK stat, and give additional effects to his attacks.
You can change character’s roles from the Set Roles submenu under the Roles section of the main menu. You can set a particular role for any character once you learn it, but only one character may use that role at a time. When you set a role for one character that is already in use on another, the role will automatically be removed from the previous character.
You can unlock new roles by having new members join your party, progressing in the story, completing sidequest, or leveling up certain other roles. Simply unlocking a role, however, does not allow you to use it. You must first expend the requisite number of skill points to learn it.
The roles active at the conclusion of a battle become honed, and they level up after a certain amount of honing. In addition, you may level roles up by expending skill points. This may be done by selecting Learn Roles under the Roles section of the main menu.
Take note that nothing’s wasted if you spend skill points in a role that’s already being honed. For example, a fresh, un-honed role costs 1000 SP to level up. If that role is already 20% honed, the SP cost will go down to round 800, and so on.