Cox was an eyewitness to the events. And he had both complimentary, and critical, things to say about Rosecrans:
"In a few moments an orderly came in some haste, saying the general desired to see me at his tent. As I walked over to his quarters, another shot was heard. As I approached, I saw [Rosecrans] standing in front of his tent door, evidently much excited, and when I came up to him, he said in the rapid, half-stammering way peculiar to him at such times: “The enemy has got a battery on Cotton Mountain opposite our post, and is shelling it! What d'ye think of that?” The post at the bridge and his headquarters were connected by telegraph, and the operator below had reported the fact of the opening of the cannonade from the mountain side above him, and added that his office was so directly under fire that he must move out of it. Indeed he was gone and communication broken before orders could be sent to him or to the post.
The fact of the cannonade did not disturb me so much as the way in which it affected Rosecrans. He had been expecting to be attacked by Lee in front, and knew that McCook was exchanging shots across the river with some force of the enemy at Miller's Ferry; but that the attack should come two miles or more in our rear, from a point where artillery had a plunging fire directly into our depot of supplies and commanded our only road for a half-mile where it ran on a narrow bench along New River under Gauley Mountain cliffs, had been so startling as to throw him decidedly off his balance. The error in not occupying Cotton Mountain himself was now not only made plain, but the consequences were not pleasant to contemplate.
I saw that the best service I could render him for the moment was to help him back into a frame of mind in which cool reasoning on the situation would be possible. I have already stated the contrast between my own sense of care when in sole command and the comparative freedom from it when a senior officer came upon the field; and I now realized how much easier it was for a subordinate to take things coolly. I therefore purposely entered into a discussion of the probabilities of the situation, and drew it out at length enough to assist the general in recovering full control of himself and of his own faculties."
...
"An hour or two passed and the detachment from Benham's brigade approached. It was the Thirteenth Ohio, led by one of its field officers , who halted the column and rode up to General Rosecrans for orders. The general's manner was still an excited one, and in the rapidity with which his directions were given the officer did not seem to get a clear idea of what was required of him. He made some effort to get the orders explained, but his failure to comprehend seemed to irritate Rosecrans, and he therefore bowed and rode back to his men with a blank look which did not promise well for intelligent action."
And again, I didn't ask anything about Iuka.