Rokocoko, 19, opened the scoring early in the final when a huge step off the left foot set him clear and he galloped home unchallenged from 60 metres out.
"We've cut his hair to reduce wind resistance," joked winning captain Damian Karauna, standing in for the suspended Dallas Seymour.
Lucas Borges hit back for the Pumas with a try in the corner after a clever kick-and-chase.
On the stroke of half-time, Rokocoko broke again from his own half and passed inside for Masoe to sprint clear and score to give the Kiwis a 14-5 cushion at the break.
Gordon Tietjens' men showed their mettle by keeping cool heads and holding out to the final whistle to earn their fourth title of the current IRB World Sevens Series.
"That was an outstanding effort," Tietjens said. "I'm really proud of my players."
Karauna talked of how so many teams have improved: "Everyone's catching up, so we have to train harder and find new ways to beat them."
They had hung on in the semi-finals to defeat Hong Kong champions England 19-10 with a late try from Nick Evans sealing victory.Masoe and Raoma had given the Kiwis an early 12-0 lead, but Ben Gollings scored the try of the tournament for England just before half-time. The Harlequins fullback, back-peddling from scrum pressure on his own 22, raced in a big arc around the New Zealanders before setting off down the wing. He then needed two kick-and-collects to get past the cover defence and score.
After the break, Anthony Tuitavaki went to the sin-bin for a high tackle, and England forced a second try through Newcastle's Jamie Noon in the corner. England then pressed hard for the winning try, but as their chances went begging Evans thumped the ball high and far and latched onto the bounce to touch down.<>In the first semi-final, a terrific try after the hooter from Martin Schusterman had earned Argentina a 22-19 victory over Australia. Peter Miller's hat trick of breakaway tries appeared to be enough for the Australians, who had the chance to boot the ball into touch when leading 19-17 but opted to run the ball. Schusterman then backed himself and charged through two tackles to reach the line.
Fiji beat a severely weakened Samoan team 64-5 in the Plate final as youngster Nasoni Roko picked up three tries.
Wales won the Bowl while Korea took home the Shield.