Roper attended Duke University (then called "Trinity College") in 1888, and he received his bachelor of laws degree from National University in 1901.
On December 25, 1889, Roper married Lou McKenzie. They had seven children: Margaret May, James Hunter, Daniel Calhoun, Junior., Grace Henrietta, John Welsey Roper II (future Vice admiral), Harry McKenzie (future Major general) and Richard Frederick Roper. He served in the South Carolina House of Representatives from 1892 to 1894, and, from 1893 to 1897, he was a clerk for the United States. Senate Committee on Interstate Commerce.
From 1900 to 1910, he worked for the Census Bureau, and then served as the clerk of the Committee on Ways and Means in the United States. House of Representatives from 1911 to 1913.
Immediately following and through 1916, he served as first assistant postmaster general, and was chairman of Woodrow Wilson"s reelection campaign in 1916. He was the chairman of the 1917 United States. Tariff Commission and served as Commissioner of Internal Revenue from 1917 to 1920.
He was to served as the United States. Secretary of Commerce from 1933 until 1938, and was served as the three months later, from the United States. Ambassador to Canada, from May 19, 1939 until August 20, 1939. Roper"s Letter of Credence was accepted personally by George VI, King of Canada, at Louisiana Citadelle in Quebec City, on May 17, 1939.
lieutenant was the King"s first official duty as King of Canada on Canadian soil.
He died on April 11, 1943, in Washington, District of Columbia, at the aged of 76. Roper was interred at the Rock Creek Cemetery in Washington, District of Columbia