James Roantree was born in 1835 in Dublin, Ireland, and later immigrated to the United States. He enlisted in the U.S. Marine Corps on January 15, 1858, in Brooklyn, New York, and served aboard the sloop-of-war USS Oneida during the U.S. Civil War. Sgt Roantree was awarded the Medal of Honor on December 31, 1864, for action aboard the USS Oneida during the Battle of Mobile Bay on August 5, 1864. He received an honorable discharge from the Marine Corps in December 1870, and died on February 24, 1873. James Roantree was buried at the New Calvary Cemetery in Mattapan, Massachusetts.

His Medal of Honor Citation reads:

On board the U.S.S. ONEIDA during action against rebel forts and gunboats and with the ram TENNESSEE in Mobile Bay, 5 August 1864. Despite damage to his ship and the loss of several men on board as enemy fire raked her decks and penetrated her boilers, Sergeant Roantree performed his duties with skill and courage throughout the furious battle which resulted in the surrender of the rebel ram TENNESSEE and in the damaging and destruction of batteries at Fort Morgan.