Rongowhakaata Pere Halbert was born at Waerenga-a-hika, near Gisborne, on 2 February 1894, the only surviving son of Hetekia Te Kani Pere (or Halbert), a farmer, and his wife, Riripeti Rangikohera Ranginui. He was of Te Aitanga-a-Māhaki and Rongowhakaata descent, and also of Te Whakatōhea. He was the grandson of the politician Wī Pere, and the great-grandson of the early Poverty Bay trader Thomas Halbert and his fourth wife, Riria Mauaranui.
Halbert attended primary school in Gisborne. He then went on to Gisborne High School, before attending Nelson College from 1911 to 1914. By this time he had reclaimed his original family name and was known as Rongowhakaata (or Rongo) Halbert. A prefect, he excelled at sports and was a member of the First XV rugby team from 1911 to 1913.
Rongo Halbert's interest in music, which was encouraged by his stepmother, Taraipine Tutaki Tamatea, also blossomed at Nelson College. He learnt to play virtually every instrument in the school's orchestra, but especially loved the cello and viola; at school concerts he gave solo piano performances. He was also a fine singer, performing as a soloist, in duets, trios and in a Māori vocal quartet.
As a young man Halbert worked for some years with the accounting firm of McCulloch, Butler and Spence in Gisborne, before joining the Native Department. On 11 September 1915, at Gisborne, he married Patehepa (Pat) Tamatea, the daughter of Mohi Tamatea of Waituhi, and his wife, Mere Te Paea Watts of Te Reinga. Rongo and Pat were to have seven children. For a time they ran a dairy farm at Pukepapa, near Waituhi.
Halbert became a licensed interpreter in 1915, and was later secretary of the Tairāwhiti Native Interpreters' Association. As early as 1918 he was representing his people at major hui. He was a member of the Tākitimu Māori Council from 1928 to at least 1946. During the Second World War he was secretary of the Gisborne branch of the Māori War Effort Organisation.
A strong advocate of Māori land development, Halbert was secretary of the Waihīrere Māori Land Blocks Incorporation. He served on a number of similar bodies, including the important Mangatū Incorporation, which, under his chairmanship (1943–49), moved from administration by the East Coast commissioner to full Māori control through the owners' management committee. From 1938 to 1968 he was a trustee of the Wī Pere Trust Estate, the family trust for his grandfather's descendants.
From 1940 Rongo Halbert devoted most of his life to studying the history and genealogy of Māori tribes, particularly those of the Gisborne, East Coast and Bay of Plenty regions. His command of the Māori language, especially written, was outstanding. On the death of Sir Apirana Ngata in 1950, he was appointed a member of the Māori Purposes Fund Board. Described as an 'equally competent scholar' and 'an eminent authority on Māori literature', Halbert was part of the revision committee that produced the sixth edition of H. W. Williams's Māori dictionary. He was an adviser on Māori texts for the Polynesian Society and assisted the New Zealand Geographic Board with Māori placenames. He served on the Māori Purposes Fund Board until ill health forced his retirement in 1968.
A founding member of the Gisborne Art Gallery and Museum in 1955, Halbert was the first chairman of the Māori Museum Committee, which advised on the establishment of its Māori collections. As chairman, he raised funds to have Hēnare Pōtae's carved meeting house returned to the East Coast from Canterbury Museum. He also served as secretary of the Tairāwhiti Māori Association and was a member of the Waerenga-a-hika Trust Board. In particular, Halbert was an active supporter of the Whakatāne and District Historical Society, his main contributions being papers on the dating of Māori genealogies, and the society's first memoir, Te Tini o Toi.
Rongo Halbert was the main Māori adviser to the Department of Education at Gisborne and to the Gisborne Borough (later City) Council; his expertise was especially sought in the correct spelling of placenames, and providing names for new schools and places. He had a special skill and knowledge in the work of the Native (later Māori) Land Court, and late in life, when he was confined to bed, the court adjourned to his home to hear his evidence in an important case. Another of Halbert's great interests was sport. He was a very keen golfer, and was involved in the administration of Māori golf, tennis and hockey in the Gisborne district. Standing over six feet tall, he was a humorous man with a quiet, gentle smile and warm, friendly eyes.
Rongo Halbert died on 11 April 1973 at Lavington Private Hospital in Epsom, Auckland, and was buried at Taruheru cemetery, Gisborne. He was survived by three daughters and three sons; his wife Pat had died the previous year. At the time of his death Halbert was preparing a major historical and genealogical work. He left three main collections of papers: a manuscript called 'Horouta', which he described as 'a comprehensive history of the Māori people of the Tairāwhiti district of the North Island'; 130 complete whakapapa charts to support the manuscript; and a series of maps recording references, placenames, battles and land blocks, with iwi, hapū and whānau names.