Rosecrans is a problematic guy. Had some part of undoubted genius to him (at the start of the war, Grant thought the three great men for the Union would be McClellan, Buell and Rosecrans). Was a huge pain to his superiors and had constant disputes with them. Loved by many of his troops, ran roughshod over immediate subordinates. Looks like an uncooperative, unreliable comrade out for himself if you have the command next to his (like Grant at Vicksburg when Rosecrans is in Middle Tennessee). Probably caused the defeat at Chickamauga by his treatment of Wood beforehand (although Wood should, IMHO, have seen a court-martial for his own part in that).
Before Varney, the last major book on Rosecrans was The Edge of Glory by William Lamers, 1961. I read that one way-back-when. Even Rosecrans biggest biographer, Lamers, thought Rosecrans' personality and behavior was the root cause of his problems. Unfortunately not a unique problem among leaders, military or otherwise, which is why Greek tragedy is based on people with fatal flaws that lead to their own destruction.