Harrison Roberts was born around 1840 in New Haven, Connecticut, to George and Hope Roberts. His father was a spinner who owned $500 of real estate by 1850. The family moved to Seneca Falls, New York, in the 1840s, and Roberts grew up and attended school there. Around 1855, he began working as a machinist at the Silsby Fire Engine Works. He moved to Chicago, Illinois, around 1858 and earned a living as a stoker in a fire department.
He enlisted in the Union army on August 7, 1862, and he mustered in as a private in Battery A of the 1st Illinois Light Artillery later that day. According to his service records, he was 5 feet, 7 inches tall, with dark hair and hazel eyes. The regiment took part in Vicksburg campaign, the Battle of Kennesaw Mountain, and the Atlanta campaign. He was promoted to 1st lieutenant on July 23, 1864, and he mustered out on July 10, 1865.
Roberts returned to Seneca Falls after the war, and he earned a living as a machinist in a fire department. He married Sarah Frances Babcock around 1866, and the couple apparently had no children. By 1870, he owned $900 of real estate and $300 of personal property by 1870. He applied for a federal pension in June 1897 and eventually secured one. His wife died in the early 1900s, and Roberts died in Seneca Falls on July 26, 1921.