Rosh Leaman was born on December 21, 1854, in Lancaster County, Pennsylvania, to Henry and Catharine Leaman. His father was a farmer who owned $27,000 of real estate and $1,960 of personal property by 1860. Leaman grew up and attended school in Paradise, Pennsylvania. He attended Lafayette College for a year before transferring to Franklin and Marshall College. By 1880, he was studying medicine in Philadelphia, Pennsylvania, and living with his brother Henry. He married Eliza Lee on September 7, 1887, and their daughter Natalie was born around 1890. They lived in Philadelphia, and Leaman worked as a doctor. He died there of “chronic heart disease” on January 26, 1917.