In 2012, Leakee became a main eventer in singles competition, and he pinned Florida Heavyweight Champion Leo Kruger during a tag team match on the January 8 episode of FCW television. On the February 5 episode of FCW television, he defeated Dean Ambrose and Seth Rollins in a triple threat match to become the number one contender to the FCW Florida Heavyweight Championship. He failed to win the championship when he lost to champion Kruger the following week. Leakee later won the FCW Florida Tag Team Championship with Mike Dalton, before dropping it to CJ Parker and Jason Jordan.
When WWE rebranded FCW as NXT Wrestling, Anoa'i, with the new ring name of Roman Reigns, made his WWE NXT debut on the October 31, 2012, episode, defeating CJ Parker.
The Shield then quietly ended their association with Punk while beginning a feud with John Cena, Ryback, and Sheamus that led to a six-man tag match on February 17 at Elimination Chamber, which The Shield won. The Shield had their first Raw match the following night, where they defeated Ryback, Sheamus, and Chris Jericho. Sheamus then formed an alliance with Randy Orton and Big Show to face The Shield at WrestleMania 29, but The Shield emerged victorious in their first WrestleMania match. The following night on Raw, The Shield attempted to attack The Undertaker but were stopped by Team Hell No. This set up a six-man tag team match on the April 22 episode of Raw, which The Shield won. On the May 13 episode of Raw, The Shield's undefeated streak in televised six-man tag team matches ended in a disqualification loss in an elimination match against Cena, Kane and Bryan.
On May 19 at Extreme Rules, Reigns and Rollins defeated Team Hell No in a tag team tornado match to win the WWE Tag Team Championship. They made their first televised title defense on the May 27 episode of Raw, defeating Team Hell No in a rematch. On the June 14 episode of SmackDown, The Shield's unpinned/unsubmitted streak in televised six-man tag team matches came to an end at the hands of Team Hell No and Randy Orton, when Daniel Bryan submitted Rollins. Reigns and Rollins defeated Bryan and Orton at Payback to retain the WWE Tag Team Championship. Further successful title defenses followed against The Usos on July 14 during the Money in the Bank pre-show and The Prime Time Players (Darren Young and Titus O'Neil) at Night of Champions. On the September 23 episode of Raw, Reigns was pinned for the first time while on the main roster courtesy of The Usos when the Shield participated in and lost an eleven-on-three handicap elimination match.
Reigns in November 2013.
In August, The Shield began working for chief operating officerTriple H and The Authority. On the October 14 episode of Raw, Reigns and Rollins lost the WWE Tag Team Championship to Cody Rhodes and Goldust in a No Disqualification match, following interference from Big Show. At Hell in a Cell, Reigns and Rollins failed to regain the tag team title in a triple threat match. Tension began to appear within The Shield, especially between Reigns and Ambrose, as Ambrose was the only member left with a championship. At Survivor Series, Reigns was the sole survivor for his team in the traditional five-on-five elimination tag team match after eliminating four opponents. After losing to Punk in a handicap match at TLC: Tables, Ladders & Chairs, Reigns defeated Punk in a singles match after a distraction from Ambrose on January 6, 2014, making him the only member of The Shield to have beaten Punk. After Punk left WWE, he recalled that he was constantly reminded to make Reigns look "really, really strong" in the match at TLC despite the Shield being scripted to lose. At the Royal Rumble pay-per-view, Reigns entered the Rumble match at #15, and set the record for most eliminations in a single Rumble with 12. He eliminated both his Shield teammates, and was the runner-up in the match after being eliminated by Batista. The next night on Raw, The Shield competed in a six-man tag team match against Daniel Bryan, Sheamus, and John Cena, with all three members of the winning team qualifying for the Elimination Chamber match for the WWE World Heavyweight Championship. The Shield lost the match via disqualification after The Wyatt Family interfered and attacked Cena, Bryan, and Sheamus. The Shield wanted revenge and a six-man tag for The Shield against The Wyatt Family at the Elimination Chamber pay-per-view was arranged, in which The Shield lost. Despite more tension, The Shield reconciled in March.
In March, The Shield began feuding with Kane, which turned all members of The Shield into faces (fan favorite characters). Over the next few weeks, The Shield continued exchanging assaults with Kane, who was joined by the New Age Outlaws, leading to a match between the two teams at WrestleMania XXX, which The Shield won. The feud with Kane also prompted The Shield to sever ties with Triple H, who reformed Evolution to counter them. The Shield defeated Evolution at both Extreme Rules and Payback. When Batista left Evolution in June, Triple H initiated "Plan B"; this involved Rollins turning on The Shield and aligning himself with Triple H.
Reigns and Ambrose subsequently quietly disbanded, with Reigns using new entrance music and later, modified tactical vest. On the June 16 episode of Raw, Reigns goaded Vickie Guerrero into adding him to the battle royal to qualify for a spot for the Money in the Bank ladder match for the WWE World Heavyweight Championship at Money in the Bank; he won by eliminating Rusev. At Money in the Bank, Reigns failed to win the title. At Battleground, Reigns participated in the fatal four-way match for the WWE World Heavyweight Championship, which Cena won to retain the title. The following night on Raw, Triple H had planned on announcing Randy Orton as the number one contender for the WWE World Heavyweight Championship, but Reigns attacked Orton, causing Triple H to lose faith in him and replace him in the title match. This prompted a feud between Reigns and Orton which culminated with Reigns defeating Orton at SummerSlam.
On September 20, 2014, Reigns underwent emergency surgery on an incarcerated hernia. WWE subsequently stated that Reigns was expected to recover in six weeks. During his recovery period, he appeared in televised interview segments; his speech delivery was criticised as "forced" by James Caldwell of the Pro Wrestling Torch in November 2014. Reigns returned to television on the December 8 episode of Raw when WWE awarded him the 2014 "Superstar of the Year" Slammy Award. Reigns made his official return six days later at TLC: Tables, Ladders and Chairs, where he prevented Big Show from attacking John Cena during the table's match with Seth Rollins, as well as attacking Rollins which allowed Cena to win the match. Reigns would return to Raw a day later to attack Fandango and Big Show. He would return to SmackDown a day later to compete in his first match in his return, defeating Fandango.