I strongly feel that Susie is a Rogue of Hope. In this case, the thievery inherent to the Rogue class would manifest as Susie's simultaneous acceptance of her role as the second hero, and complete disregard for the less favorable parts of the prophecy that bestows that role upon her. Hope derived from the prophecy does not belong to her, but she takes it anyway, spit-shines it, and hands it off to her friends. She has total, unwavering faith in her party's ability to circumvent the Last Prophecy.

When Susie forces Ralsei to learn R-Action, it makes total sense as a step in his personal character arc, but he attempts to reject it, since he's not "supposed" to be able to act on his own. The development Susie causes Ralsei to have comes at the direct cost of adherence to his prophesied role. Susie's very own defiance of her role as a brutish attacker comes in the form of her learning healing magic; the literal ability to heal her friends is something she was not supposed to have, let alone excel at. Bear in mind that Ralsei only agrees to teach Susie to heal after she teaches him R-Action - she causes him to loosen up on the prophecy, at least a little. As for the way her classpect shines through in her relationship with Kris... for the sake of brevity, I'll allow this dialogue from the end of Chapter 4 to speak for itself:

"
* (Susie's smile, which

seemed to defeat everything)

* (Shined on in front of you,

and for a moment)

* (It was as if all

the darkness had been

blown away.)

* (As if in imitation,

your SOUL began to glow...)
"

Also, I think Kris is a Knight of Heart, but that's not very groundbreaking.