He was born in England, but his family moved to New Zealand when he was six months old. His father, a graduate of Christ Church, Oxford, was a professor at Canterbury College in Christchurch. Roger was educated at Christ’s College, Christchurch, where he captained the First XI cricket team.
A batsman and leg-spinner, he began his first-class career at 17 on Christmas Day 1917 for Otago against Canterbury at Christchurch, taking six wickets. He was a prolific batsman in domestic cricket throughout the 1920s, playing several representative matches for New Zealand against Australian and English teams in the days before New Zealand played Test cricket. When New Zealand made its first major overseas tour, to England in 1927, he scored 1540 runs at 44.00 and took 77 wickets at 25.29, and in recognition of these performances he was chosen as one of the Wisden Cricketers of the Year in 1928.
In New Zealand’s first Test, against England in Christchurch in January 1930, he made more runs and took more wickets than any other New Zealander (45 not out and 7; 3 for 17 and 2 for 17) as New Zealand lost by 8 wickets. He played in all of New Zealand’s first nine Tests: four against England in 1929-30, three against England in 1931, and two against South Africa in 1931-32. His highest Test score was 96 against England at Lord’s in 1931.
Batting for Otago against Canterbury in Christchurch in 1931-32, he made 338 not out at a run a minute out of a total of 589 all out, in a match that Otago nevertheless lost. It was the highest first-class score by a New Zealander until Bert Sutcliffe beat it with 355 in 1949-50. Blunt’s best first-class bowling figures were 8 for 99 for Otago against Auckland in Dunedin in 1930-31.
After the 1931-32 season he played no further cricket in New Zealand, but did appear in three minor first-class matches in England in 1934 and 1935.