Born in Arad, Kingdom of Hungary, Austrian Empire (modern-day Romania), in 1854 as Franz Denta, son of an army NCO, he became a lieutenant in the 3 Galizisches Uhlanen-Regiment Erzherzog Carl in 1876 upon graduating from the Theresian Military Academy in Wiener-Neustadt.

Having attained the rank of Colonel, he was appointed Chief of Staff of II Corps in September 1897, a position in which he served until April 1901.

[2] Having overseen the successful defense of the Carinthian frontier, Rohr was promoted to the rank of Generaloberst on January 1, 1916, and made commander of the new 10th Army following the dissolution of his army-group in anticipation of the Tyrol Offensive.

[3] In February 1917, and with the promotion of Gen. Arz von Straussenberg to the position of Chief of the General Staff, Rohr took charge of the 1st Army and for the first time served as a commander on the Eastern Front.

Promoted to the position of Field Marshal on January 30, 1918, Rohr continued in command of the 1st Army until its disbandment following peace with Romania on April 15, 1918.