Kingdom Hearts II Final Mix
Roxas possess extraordinarily high magic defense, and as such, Sora should not rely on offensive magic other than Reflect in this fight for defensive purposes. Even if Reflect deals damage to Roxas, it will only deal roughly 1/10th worth of damage to one of Roxas's HP bar.
The battle will always begin with Sora directly in his attack range. Just as the battle commences, Roxas will immediately use a variation of Whirlwind Swing that covers a large portion of the field. He will then run behind Sora and use either Aerial Spin Swing, Whirlwind Swing, or Continuous Swing. Roxas may use Duel Attack every now and again, and should Sora win, will start using Spot Beams and Arranged Beams relentlessly until he gets the chance to close in and use Instant Recapture Attack.
When Duel Attack is completed successfully, several of Sora's actions (not just his attacks) all have Roxas's stolen Keyblades react each in a special manner dependent on the type of move Sora performs (such as spiraling around him during ground combos or piercing through Roxas from multiple directions if he gets launched into the air). However, this may also cause Roxas to retaliate sooner as more specific types of hits are landed on him, so be wary of being combo-happy on him. Eventually, he'll perform his Instant Recapture Attack and inevitability reacquire his stolen Keyblades, so while Sora has Roxas's Keyblades in his possession take advantage of the situation in a careful and quick manner, dealing as much damage on him as possible while avoiding retaliation. When Roxas attempts to retake his Keyblades, Sora can quickly use Reversal to escape his counterattack, but failure will result in Roxas knocking Sora away for heavy damage. Either way, both results will end up with Roxas's Keyblades back in his hands.
After a quarter of his health is gone, Roxas gets even more aggressive. Duel Attack is used less frequently, and Roxas also adds several light-based elements and extra beams during several of his actions, causing him to have a more erratic attack range. Be on guard and do not try to block on misjudgment if possible (due to the light beams being unblockable), as Roxas's physical moves can still be blocked and countered normally.
However, regarding moves that come with the beams, it's possible to have Roxas turn around if Sora ends up behind him, altering the locations of the beams and allowing for easier room to block his physical attacks. Blocking any of his physical moves will at least always allow Sora to bypass his beams with Guard's invincibility from successful blocking.
Once he is down to 40% of his HP, Roxas enter his desperation state will use his "Keyblade Release" attack frequently, and light beams will even be launched simply from him dashing around.
If Roxas is knocked into the air during his retaliation point, he will retaliate with an Aerial Spin Swing. However, on ground he'll retaliate with random moves if Sora lets up on his assault somehow, especially during the later phases after using his desperation move, Keyblade Release.
In the data rematch, Sora should use exactly the same strategy he used when taking down his Nobody in the World that Never Was, but there are some differences, apart from Roxas's higher HP.
Roxas retaliates sooner from Sora's combos, and can now retaliate after just one finisher, though it may be hard to tell if Sora has Finishing Pluses and uses them on his Nobody. The projectiles in Keyblade Release now fly at faster speeds, requiring Sora to use Glide (Quick Run and Dodge Roll are not as advised due to the recovery on such movement options) to evade them. The best strategy is to activate (and win) his Duel Assault whenever possible to steal the Oathkeeper and Oblivion and bombard Roxas continuously. As long as Sora heals when necessary, the battle can be cleared with few problems.
Another method is to use Limit Form and use Sonic Rave constantly; Sora will heal back the bits of damage he is dealt in between the limits, and do decent damage. Strike Raid is not advised due to the inconsistent invincibility frames, and as it puts Sora in a stationary position; Infinity and Last Arcanum however, work wonders provided if Sora can connect onto Roxas properly, with the latter being exceptionally solid if Sora drops the extra Reaction Commands to prevent Roxas from reaching his retaliation point sooner than usual.
Kingdom Hearts coded
Main Article: Game:Data-Roxas