A 24-10 defeat by New Zealand last Saturday has left England knowing they must beat last season's Four Nations winners at Melbourne's AAMI Park this weekend to stand any chance of reaching the final.
In stark contrast to their match against the NZ Maori two weeks ago, when they raced into an 18-0 half-time lead, England started slowly last Saturday before rallying after the break and Roby is acutely aware they must show the best of both worlds on Sunday.
"We have to show what we are capable of," he said. "We have flown all this way to try and win the competition and this weekend is a perfect opportunity for us to show what we can do.
"There are no excuses, we know that if we don't win this weekend we will be going home before the final and nobody wants to do that.
"We're going to train hard all week and carry on working for each other.There's a great spirit amongst this group of players and a lot of ability.
"We know that if we put in the performance we are capable of the result will take care of itself.
"All the lads are looking forward to it because they see it as a chance to build on the good form we showed in the second half last week."
Sunday will see Roby come up against a player widely regarded as the world's best hooker and the St Helens No 9 is relishing the challenge.
"You want to test yourself against the best players and Cameron Smith is regarded as one of the greatest players in the world so it's going to be a good challenge," he said.
"We will look at what he does well and not-so-well during our preparation but it's not about individual battles, it's about a strong team performance. As long as we come out on top, that's all that really matters."
Roby is not unduly concerned by the nature of England's opening to last week's match in Wellington, where they conceded three first half tries without reply, and insists there is no need to panic.
"It was a much more intense game than the warm-up games we played," he said. "It's a different kind of game over here, you have to be more patient, complete our sets and in a way be a little more boring.
"We didn't stick with it at times last Saturday and let ourselves down. We know we can't afford to make the same mistakes again.
"We will look at what went wrong and rectify everything in time for Sunday. It's an eight-day turnaround and we have plenty of time for some high quality preparation."
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