Rowntree feels end-of-season fatigue has been cited as the reason for too many summer failures in the past and expects all the players to be firing come kick-off at Durban's Kings Park on Saturday.
England have certainly enjoyed a thorough preparation for the three-Test series with most of the squad having been in camp a fortnight and training in South Africa for more than a week.
Rowntree said: "In recent times on these tours, at the end of a long season, you have used every excuse going.
"But then we won the second Test in Australia two years ago.
"We need to build more of that into our game now.
"We have got to start winning these big games. Our season only finishes on June 24."
Rowntree is well aware of the ferocity of the challenge likely to face England from the Springboks.
South Africa are renowned for their physicality and, even with three new caps in their pack, they still boast a formidable front row.
Loosehead Tendai Mtawarira comprehensively and infamously outplayed former England captain Phil Vickery in a British and Irish Lions Test three years ago while Bismarck du Plessis is regarded as one of the world's top hookers. His brother Jannie du Plessis completes a front trio that all play together for Durban-based Sharks.
Rowntree remembers the Lions clashes well having worked as scrummaging coach for that series.
He said: "I am a big fan of their front row.
"We all saw what 'The Beast' [Mtawarira] did last time I was here, Bismarck has got exceptional skill and I like that in a player. Then there is Jannie as well.
"They are a challenge for us but as a forwards connoisseur I am looking forward to that battle.
"We saw it in the Lions' first Test and in the second Test we rectified that. That battle tomorrow will be very interesting."
England are looking to build momentum after an encouraging campaign under new head coach Stuart Lancaster in the RBS 6 Nations, which raised spirits after a poor World Cup.
England, with new captain Chris Robshaw at the forefront, lost only one Six Nations game.
Robshaw, who has just six caps to his name, said: "We have spoken about the teams and the players and this is another step up.
"We look at where we were in the Six Nations and we are now coming away from home and we are building on what we have achieved so far.
"Of course we have got to match them but it is about playing our game."
As thorough as England's preparations have been, Robshaw knows that any game plan might have to be adapted as the matches progress.
The 26-year-old said: "We have been watching a lot of Super 15, of course, but whenever you play any game they [opponents] are going to have some tricks.
"It is also about reacting to certain situations. You can't prepare for everything, you have to hope players are good enough to think on their feet."
England will welcome two new players into the side for the opener in Exeter flanker Tom Johnson and Robshaw's Harlequins team-mate Joe Marler, the loosehead prop.
Robshaw said: "I think Joe has done himself a huge amount of credit this season and has risen to every challenge that has been thrown at him.
"He is going to enjoy it. Everyone, I think, will be looking forward to it."
Johnson's chance comes after a fine season for Aviva Premiership surprise package Exeter.
Rowntree said: "The new faces in the team thoroughly deserve their chance.
"Tom Johnson has been exceptional in recent weeks.
"There are new names coming into the team and that makes it more exciting."
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