The Robins take on the Millers on Wednesday evening (October 3rd, 7.45pm kick-off), off the back of the 1-1 Friday night draw at home to Aston Villa.
The match allowed City to rest up over the weekend, before preparations resumed as normal on Monday morning.
“Weve had a good amount of time to reflect and review, more importantly” Johnson said ahead of the trip to the New York Stadium.
“There were some brilliant elements, particularly in the first half, the way we penned Villa in; we didnt give them much of a sniff but when we did it was down to not clearing the ball properly.
“We put good crosses in and we limited a very good set of individuals to nothing apart from the goal and that was the disappointing thing.
“But we rallied quite well and that stands us in good stead going into another important game, to try and be successful in it.
“We had the extra day and with this being a Wednesday it has been good to give the weekend to the lads.
“With a midweek game preparation differs slightly because the boys get a bit of extra rest of the weekend. A group went in to train and a group were off so hopefully that will stand us in good stead for Wednesday, to play with good energy.
“I expect a high-energy game, similar to the Wigan game where we worked our socks off for each other.
“They (Rotherham United) will be difficult to break down and they have threats but we concentrate on our own game and that is what was pleasing about our performance against Aston Villa. We showed the levels of desire and commitment that the supporters deserve and we need to take that mindset into Wednesdays game because undoubtedly we will have a proportion of the game and we need to capitalise on that proportion.”
Johnson also discussed his selection headache ahead of the trip to Yorkshire and the balancing act he faces between introducing new blood and keeping consistency.
“A couple arent performing as well as they can but we believe in them. Naturally everybody wants to play and naturally you want to give everybody a chance but you have to be careful not to weaken cohesion or personnel.”
That result was made even more credible by the fact that strikers Kyle Vassell and Jamie Proctor were missing, skipper Richard Wood went off injured while only remaining senior striker Michael Smith played having not trained all week.
Proctor has been ruled out for up to six weeks with a groin strain, Vassell will try and manage his knee injury while Paul Warnes medical team will see how Wood and Smith pull up early this week.
Then to make matters worse ahead of the visit of City, Zak Vyner, who is on loan from the Robins, is ineligible, leaving Warne short at the back if Wood does not make it.
This week has been difficult, we had Vas out, Proctor out and Smithy didnt train all week, Warne said. He hasnt been fit, he had a scan on his groin and he still played and put his body on the line for this team.
Vassell damaged his knee at Forest, he had a scan, he has a bit of cartilage damage but luckily he doesnt need surgery so that is dependant on his pain threshold really.
Its just a, Look at him every day, he did do a bit of light running on Friday but was in pain.
With potentially Wood, Sean Raggett and Clark Robertson all missing, Warne could play Billy Jones at right-back and Will Vaulks at centre-back, or vice-versa.
I have got no centre-halves and Zak cant play Wednesday so that is a bit of a problem, Warne added. I havent got anyone coming back prior to the game.
He said: We send them out with a smile on their face and they try to compete against some unbelievable players.