While Data-Roxas spends much of his time lurking in the shadows, bursts of his personality appear throughout the story. He is sullen and silent, dwelling on his status as a mere illusion, but is content to remain in the shadows as Data-Sora wanders throughout the worlds. He can often be exceedingly cold, thinking of the people in Castle Oblivion as mere illusions, and suggesting that Data-Sora can hurt them as much as he wants, without retaliation.
Like the real Roxas, he can be impulsive, shown when he attacks Data-Sora when he refuses to forget the people that were important to him. He can be arrogant too, unafraid to mock Data-Sora in his confusion. At the same time, he is kind enough to guide Data-Sora throughout Castle Oblivion, and knows when to resign to his fate.
Data-Roxas takes the appearance of Roxas as he appeared in the end of Kingdom Hearts 358/2 Days, wearing a Black Coat. He is seen mainly with his hood up, with his face only being seen for a brief moment after his defeat.
The bugged version of Data-Roxas is completely black, resembling a silhouette, and wields dark versions of the Oathkeeper and Oblivion Keyblades. Data-Roxas's body and Keyblades are covered and surrounded by glowing, blue panels resembling computer screens.
Data-Sora encounters a Black Coated figure in the Dive to the Heart. Although he later guesses the figure is Data-Riku, who himself initially appears in a black coat, Data-Riku informs Data-Sora that their first meeting was on Destiny Islands, leaving Data-Sora to wonder who the first figure was.
The mysterious figure appears again in Castle Oblivion, giving Data-Sora a World Card for Destiny Islands. After obtaining one of the ending cards, the figure returns to give Data-Sora the World Cards for Traverse Town, Wonderland, Olympus Coliseum, Agrabah, and Hollow Bastion.
He returns after Data-Sora obtains the first ending card for each world, mocking Data-Sora for forgetting the people that he thought were important. After at least one ending card from each world is obtained, the figure challenges Data-Sora into a fight to show him what "real hurt" feels like. After being defeated, the figure reveals himself to be a data version of Roxas, and gives Data-Sora the final World Card. At this point, Data-Roxas transfers his memories into Data-Sora, before disappearing.
A bug version of Data-Roxas can also be fought in the last System Sector at Hollow Bastion during Questploration.
Like his real counterpart, Data-Roxas wields the ability of light, and by using the ability 13 Beams, he can direct rays of light at opponents. He is also able to use the Synch Blade ability, dual wielding the Oathkeeper and Oblivion Keyblades with skill like his real-life counterpart.
His attacks with the Keyblades are almost exactly like how he fights with them in Kingdom Hearts 358/2 Days, with a few more light pillar attacks.
He is able to telepathically control his Keyblades as well, shown in his aerial combo finisher, in which Data-Roxas makes his Keyblades revolve quickly around him, before catching them again. Also shown to be highly agile, he easily performs backflips and sidesteps. Finally, when his health dwindles, he can use Roxas's limit break in Kingdom Hearts 358/2 Days, Magic Hour, causing beams of light to shower randomly from above; and also the Final Limit version of the attack, with much larger beams of light.