Roderick David Finlayson was born in Devonport, Auckland, on 26 April 1904. His father, John Maclennan Finlayson, was an accounts clerk in the Bank of New South Wales in Auckland. Because of gambling debts he absconded to San Francisco in 1905, effectively ending his marriage to Mary Milligan Cargo. She brought up her son in the home of her northern Irish mother in Ponsonby.
Finlayson attended Ponsonby Public School from 1909 to 1917 and Seddon Memorial Technical College from 1918 to 1921. He passed the City and Guilds of London Institute examination in mechanical engineering in 1921. About 1923 he was apprenticed as a draughtsman to John Anderson, an Auckland architect; his duties came to include rent collecting and selling real estate. Finlayson also began night school, passing the matriculation examination in 1924. From 1926 to 1929 he studied part time in the School of Architecture at Auckland University College for an associateship in the New Zealand Institute of Architects.
With the onset of the slump, however, Anderson's business failed and Finlayson's employment ended. After unsuccessful ventures as a travelling salesman and tobacco farmer, Finlayson took up the life of a writer in the mid 1930s. He had experimented as a writer of romance as early as 1924, and published occasional journalism in the Auckland papers. In the early 1930s he turned to satire to express his disillusionment with 'our ruthlessly technological and acquisitive society', now apparently in collapse. This disillusionment had been building for some time. About 1922, a conviction for failure to attend compulsory military drill stirred Finlayson's developing radical sympathies. Despite his Unionist family background, he was drawn to the Republican cause in Ireland. Later in the 1920s he supported Samoan aspirations for self-government.
In the 1920s, too, he came to repudiate his boyhood enthusiasm for science and technology. This was the result of his childhood experience of farms managed and owned by his uncle, Arthur Wilson, in the Bay of Plenty and at Glenbrook. His uncle emphatically rejected mechanisation in his husbandry of the land; he became the model for Uncle Ted in the novel Tidal Creek. Farm life also introduced Finlayson to rural Maori. He stayed with the family of Hone Ngawhika at Pukehina for several summers during the 1920s until about 1931, learning from him traditional ways of living with the land.
In 1934 or 1935 Finlayson met the poet D'Arcy Cresswell, whose radio broadcasts he admired for their excoriation of science and modernity. He became a frequent visitor to Cresswell's Castor Bay bach, where he met his future publishers Bob Lowry and Ron and Kay Holloway, as well as Frank Sargeson and other writers. Finlayson showed Cresswell his satiric writing, but Cresswell was more impressed by some short stories, modelled on those of the Sicilian writer, Giovanni Verga. These were written about the Pukehina community from which Finlayson now felt himself to be in exile, possibly as the result of a failed love affair. Cresswell became his literary mentor, a role later shared with Sargeson; he recommended his friend's work to publishers, and provided him with exacting criticism.
Cresswell acted as best man at Finlayson's marriage to Ruth Evelyn Taylor in Auckland on 3 June 1936. He had met her when he holidayed in Rarotonga, her birthplace, in 1931. The couple moved to Weymouth, on the Manukau Harbour, in 1937, and there they raised three daughters and three sons.
The war years, during which Finlayson served in the Home Guard and worked in a woolstore under emergency regulations, brought him new friendships, including that of the younger writer David Ballantyne. It was also a time of spiritual discovery: brought up a Presbyterian, Finlayson converted to Catholicism in 1949.
He had his greatest success as a writer from 1938 to 1952. He won third prize in the short story section of the centennial literary competitions with 'The totara tree'. Cresswell wrote to him in the early 1940s, 'Men like you & Sargeson are founding our native style, if we are to have any.' Although eclipsed by Sargeson, Finlayson participated in the emergence of a regional literature that seemed to be revealing the country to itself, critically, for the first time. He shared the romanticism of many of his contemporaries, celebrating what he called the poetic life, 'a life dependent on the forces and powers of Nature', and lamented its loss in the kainga (village), on the farm, within the human heart. Finlayson developed his romantic thesis in polemical essays, notably Our life in this land (1940), and it informs his fiction: the short story collections Brown man's burden (1938) and Sweet Beulah Land (1942), and the novels Tidal Creek (1948) and The schooner came to Atia (1952).
Roderick Finlayson's distinctive contribution to the writing of New Zealand was the Maori stories of his first two collections. They portrayed a people caught between two worlds, as the urban economy insinuated its influence into traditional communities, bringing Pakeha bent on their dispossession. Although his rendering of Maori thought and speech has sometimes been criticised as simplistic, Finlayson's sympathetic yet unsentimental stories make him an important transitional figure between the colonial apologia of precursors such as A. A. Grace and the Maori writers who have succeeded him.
From 1952 to 1960 Finlayson wrote almost entirely for children; he was commissioned by the School Publications Branch of the Department of Education to produce stories on Maori life and history, and on his own childhood. The Maori historical fiction was republished as The springing fern in 1965; he also wrote The Maoris of New Zealand in 1958. The work introduced Finlayson to James K. Baxter, his sometime editor; the 1950s also brought close friendships with O. E. Middleton and the Australian poet Bruce Beaver.
Finlayson had always had to supplement the meagre financial return from writing with occasional farm labour; he was also sustained by family legacies. From 1957 to 1965 he took up employment as a printing-room assistant at the Auckland City Council, and he produced little in these years. After his retirement, he published D'Arcy Cresswell, an apologia in the form of a critical biography, in 1972. Its appearance coincided with a renewal of interest in Finlayson's work, most of which was republished from 1972 to 1988. Occasional stories aside, he published one additional collection of fiction, the three novellas of Other lovers in 1976. Finlayson remained active as an essayist from the 1960s; he also campaigned on political issues, notably in defence of Maori land and language and in opposition to apartheid.
The Finlaysons toured Europe in 1972, following in the steps of D'Arcy Cresswell. Throughout the 1970s and early 1980s they also travelled regularly to Rarotonga. In 1990 Finlayson was made president of honour of the PEN New Zealand centre. His achievement as a writer was recognised by Manukau City in 1990 and 1991.
Although never in robust health, Roderick Finlayson lived until 2 August 1992, when he died at Weymouth. He was survived by his wife and children. His headstone reads, simply, 'Writer'.