To clear things up:
Sorcerer's curse - reroll all successful to hit-rolls
Expert Swordsman - reroll all unsuccessful to hit-rolls (when charging)
You cannot reroll a reroll, so what you'd have to do (theoretically) is roll all dice once, pick all up and roll them again. Some, because they were successful the first time around, some, because they weren't.
Of course, it would be easier to just say the two events even themselves out and to just roll the dice once without any rerolls.