Roy was the son of Dr. Joseph Dean Barnes (1841-1882) and Harriet Petterson "Hallie" Chew (1846-1930), who married second, Rear Admiral Francis Mackall Gunnell (1827-1922).
Roy Graduated 17th in his class at West Point in 1901. After graduation he was stationed at Fort Monroe, Virginia; Key West Barracks, Florida; Fort Snelling, Minnesota; and Fort McKinley, Philippines. He left the Philippines in 1907 for San Francisco, where he was stationed until he returned to West Point for a year as an instructor in the Department of Philosphy. Barnes made the rounds as an aide to Brig. Gen. Brush. During World War I, he served by detail in the Adjutant General’s Department in France and later commanded the 327th and 330th regiments of Field Artillery. He saw duty as a member of the General Staff in Washington, D.C. He served as Chief of Staff of the American Forces in China. Joseph retired as a colonel while a patient at Walter Reed General Hospital and died at the age of 59, only days after his retirement (findagrave.com)
findagrave.com lists a second wife, but I do not find her listed in any relevant census reports (EAD)