Kareroa was born on Rarotonga and educated at Mangaia Primary School and Mangaia College.[1] He worked as an agent for Air Rarotonga.[2] He was first elected to Parliament in the 2014 Cook Islands general election. After the election he was reportedly offered a ministerial position by Prime Minister Henry Puna in exchange for supporting him in the House, but refused.[3] He was re-elected in the 2018 election.[4]
In February 2020 he was appointed Democratic Party spokesperson on National Superannuation and Parliamentary Services.[5]