John Hemingway Roberts was born on October 8, 1831, in Alfred, Maine, to Nyman and Sally Roberts. He got married in the 1850s, and they had at least three children: Lillian, born around 1860; Gertrude, born around 1866; and Mattie, born around 1867.
In September 1861, he received a commission as a 2nd lieutenant in Company F of the 8th Maine Infantry. He was promoted to 1st lieutenant in June 1862 and to captain in August 1862. In January 1864, Union forces transferred him to the 2nd Maine Cavalry. He resigned on June 15, 1865.
He settled in Chelsea, Massachusetts, after the war, and he earned a living as a fruit dealer. His wife died in the 1860s, and he married Harriet E. Phelps on April 29, 1868. The couple had no children. By 1870, he was working as a bookkeeper, and he owned $4,000 of real estate and $1,000 of personal property. He supported the Republican Party, and he served in the state legislature in the early 1870s. He supported President Ulysses S. Grant in the election of 1872. He died of an enlarged heart in Chelsea on December 22, 1898.