Waerea-Hargreaves joined the Sydney Roosters in 2010 on a three-year deal. He was selected to play for New Zealand from the interchange bench in the ANZAC Test, in their 12–8 loss.[11] In week 1 of the finals, against Wests Tigers, Waerea-Hargreaves was on a receiving end of big hit from Simon Dwyer. The Roosters won 19–15 in golden point extra time due to a Shaun Kenny-Dowall 70-metre intercept try.[12] Waerea-Hargreaves played off the interchange bench in the 2010 NRL Grand Final, losing 32–8 to the St George-Illawarra Dragons.[13] He played in 19 matches for the Roosters in 2010. Waerea-Hargreaves played a match for New Zealand in the Four Nations, a 76–12 victory over Papua New Guinea.[14]
2011
In round 25, against the Cronulla-Sutherland Sharks, Waerea-Hargreaves scored his first club try for the Roosters in the 36–25 win at the SFS.[15] He played in 21 matches and scored a try for the season. Waerea-Hargreaves was selected in the New Zealand Four Nations squad.[16]
He played in 23 matches and scored 3 tries in 2012. Waerea-Hargreaves played off the interchange bench in the October test against Australia.[18]
2013
For the 2013 ANZAC Test, Waerea-Hargreaves played for New Zealand at prop in their 32–12 loss.[19] In round 9, he copped a 5-week suspension after being sent off for a head tackle against the Sea Eagles.[20] Waerea-Hargreaves played prop in his second grand final against the Sea Eagles, the Roosters winning 26–18.[21][22] Waerea-Hargreaves played in 21 matches and scored a try in the Roosters' successful season.
He played for the Kiwis in all 7 matches of the World Cup including the 34–2 loss to Australia in the final.[23][24]
2014
In round 11, against the Canterbury-Bankstown Bulldogs at ANZ Stadium, Waerea-Hargreaves played his 100th NRL career match in the Roosters 32–12 win.[25] In round 19, against the Penrith Panthers at the SFS, he played his 100th match for the Roosters in the 32–12 win.[26] Waerea-Hargreaves finished off the 2014 season with him playing in 26 matches and scoring a try. In December, the Canberra Raiders offered Waerea-Hargreaves a multimillion-dollar contract but ended negotiations after he failed to meet a deadline.[27][28]
2015
On 24 January, Waerea-Hargreaves was the co-captain of Roosters 2015 Auckland Nines squad alongside Mitchell Pearce.[29] On 13 February, he played for the NRL All Stars in the 2015 All Stars match. The NRL All Stars lost 20–6 to the Indigenous All Stars.[30] In round 23, against the Parramatta Eels, Waerea-Hargreaves scored one of the best solo tries of the season, scoring a crucial try by steamrolling two defenders and brushed off two more to score next to the posts in the Roosters 28–18 win.[31][32] In the next match against the Brisbane Broncos, his season ended after he suffered a knee injury.[33][34] Waerea-Hargreaves finished the year with him playing in 19 matches and scoring 2 tries.
2016
In round 9, against the Newcastle Knights, Waerea-Hargreaves made his return for the Roosters from injury, playing off the interchange bench in the 38–0 win at the Sydney Football Stadium.[35][36] Waerea-Hargreaves finished the 2016 NRL season with him playing in 14 matches for the Roosters. On 6 September 2016, Waerea-Hargreaves was added to the New Zealand national rugby league team train-on squad for the 2016 Four Nations.[37]
2017
Waerea-Hargreaves played in every game of the 2017 NRL season for the Roosters as the club fell one game short of a grand final appearance suffering a shock defeat by North Queensland in the preliminary final 29–16.[38][39]
2018
Waerea-Hargreaves was part of the Easts side which won their 4th minor premiership in 6 seasons. On 30 September, Waerea-Hargreaves played in Eastern Suburbs 21–6 victory over Melbourne in the 2018 NRL grand final winning his second premiership as a player and the roosters 14th.[40]
2019
In round 17 against North Queensland, Waerea-Hargreaves was placed on report in the club's 15–12 loss at the Central Coast Stadium after allegedly headbutting North Queensland player Josh McGuire. Waerea-Hargreaves was later cleared of any wrongdoing but was initially facing a two match ban.[41]
In round 25 against arch rivals South Sydney, Waerea-Hargreaves was placed on report after hitting Souths player Liam Knight with a late tackle around the head which left Knight bleeding on the ground. The Roosters would go on to lose the match 16–10 at ANZ Stadium.[42]
In the qualifying final against South Sydney, Waerea-Hargreaves was placed on report and later suspended for one match after being found guilty of tripping Souths player James Roberts.[43]
Waerea-Hargreaves missed the club's preliminary final victory over Melbourne but played in the 2019 NRL Grand Final where the Sydney Roosters won the match 14–8 against the Canberra Raiders at ANZ Stadium. It was the club's second consecutive premiership and the third premiership for Waerea-Hargreaves as a player.[44]
On 22 November 2019, it was announced that Waerea-Hargreaves had signed a three-year contract extension to keep him at the club until the end of the 2023 season.[45]
2020
Waerea-Hargreaves played 18 games for the club in the 2020 NRL season. They fell short of a third successive premiership losing to Canberra in the elimination final.[46]
2021
Waerea-Hargreaves played a total of 23 games for the Sydney Roosters in the 2021 NRL season including the club's two finals matches. The Sydney Roosters would be eliminated from the second week of the finals losing to Manly 42-6.[47][48]
2022
In round 24 of the 2022 NRL season, Waerea-Hargreaves was sent to the sin bin for a dangerous high tackle during the Sydney Roosters upset victory over Melbourne.[49]
In the elimination final, Waerea-Hargreaves was sent to the sin bin for a dangerous tackle in the club's upset defeat to arch-rivals South Sydney which ended their season.[50]
In the third group stage match at the 2021 Rugby League World Cup, Waerea-Hargreaves was sent to the sin bin for a stiff arm to the head of Dan Norman during New Zealand's 48-10 victory over the Republic of Ireland.[51]
2023
Waerea-Hargreaves signed a one-year extension with the club for the 2024 season. In round 26 of the 2023 NRL season, Waerea-Hargreaves was placed on report for a high tackle on Wests Tigers player Apisai Koroisau. Waerea-Hargreaves was later suspended for seven matches, which ended his season.[52]
2024
Waerea-Hargreaves announced on 20 February that he would depart the Sydney Roosters at the end of the season.[53] A day later it was announced that Hull Kingston Rovers signed the prop for the 2025 season.[54][55]
In round 10 of the 2024 NRL season, Waerea-Hargreaves played his 300th game for the Sydney Roosters in their 38-18 victory over the New Zealand Warriors.[56] Waerea-Hargreaves would go outright first for most games played for the club during their round 18 match against St. George Illawarra. Waerea-Hargreaves was sin binned during the game. Waerea-Hargreaves played 18 games for the Sydney Roosters in his final season at the club including their preliminary final defeat against Melbourne.[57][58]