Robert Josselyn was born to Josiah Josselyn (21 August 1778-30 April 1864) and Ruth Howland (25 October 1778-16 August 1848) in Pembroke, Plymouth County, Massachusetts on 16 December 1810. Their family relocated to Windsor County, Vermont about 1815. Robert later moved to Virginia, studied law, and was admitted to the bar in that state in 1831. Relocating in 1836 to Oxford, Lafayette County, Mississippi, he represented that county in the state legislature (1838-1839), before being appointed a district attorney by Governor Alexander Gallatin McNutt (03 January 1802-22 October 1848). In 1840, he moved to Holly Springs, Marshall County, Mississippi, and represented that county in 1843-1844. During the Mexican War (1846-1848), he initially served as a private in the 1st Mississippi Rifles under Jefferson Davis (03 June 1808-06 December 1889). Following the Battle of Monterrey (20-24 September 1846), President James Knox Polk (02 November 1795-15 June 1849) approved his elevation to Assistant Commissary of Subsistence, with the rank of Captain. Subsequently, he worked as State Commissioner of Mississippi (1850-1858), and as a clerk in the U.S. Treasury Department (1860).

     Josselyn was appointed Confederate Presidential Secretary on 20 February 1861 and remained in the post until formally replaced by Burton Norvell Harrison on 17 March 1862. A short lived assignment as Secretary of Arizona Territory followed. After the war, he practiced law for a year in Shreveport, Caddo Parish, Louisiana, then held editorial jobs with the State Gazette (Austin, Travis County, Texas), Dallas Herald (Dallas County, Texas) and The Statesman (Austin, Travis County, Texas). He was intended to be the first State Librarian of Texas, but like all former Confederates was barred from office in 1867 by the Reconstruction government. Prior to his death, he was selected to serve as a clerk in the office of Texas Governor (and former Texas secession delegate) John Ireland (21 January 1827-15 March 1896). Throughout his life he was a noted and published poet. Some of his works are included in the following collections: The Faded Flower and Other Poems (1849), A Satire on the Times (1873), and The Coquette (1878). Josselyn died on 04 November 1883, and is buried in Oakwood Cemetery in Austin, Travis County, Texas.