Roger Bennett Sherman was born in Lubbock, Texas on October 8, 1892. He grew up on his father's cattle ranch there, participating fully in the ranch operations. He left high school in 1913 and would not pursue further education for many years. In 1932 he married Bessie Atkinson Standhardt, a widow with two children. They had one child, named Joseph after Roger's father.
Sherman first became interested in Presbyterian missionary life through a family friend, Ralph J. Hall, who was a Mobile Minister for the Board of National Missions. In 1929 Sherman became a lay missionary for the Board of National Missions, beginning work in southern Nevada and two years later transferring to the Pecos Valley Presbytery in New Mexico, where he worked side by side with Hall. Sherman was influential in developing a rancher's camp meeting type of ministry during these years. Despite his lack of seminary training, he was ordained in the Little Grey Church in Dexter, New Mexico on October 29, 1939. As an ordained minister, he was able to perform marriages and baptisms in the isolated ranches of his territory.

In 1941, Sherman was accepted for admission to the College of Christian Education in Chicago, but left after two months of study when his stepdaughter died. He never earned a degree.