Roberts and company mounted an heroic rearguard throughout much of a Millennium Stadium contest that England dominated with regard to possession and territory.
Not since they shut out Scotland at Murrayfield six months ago had Wales managed to prevent their opponents from scoring a try.
And while an England team alarmingly devoid of flair or imagination only had themselves to blame in many respects, Wales proved Shaun Edwards' mantra that defences win matches.
Edwards, Wales' defence specialist, could not have scripted a more resilient performance if he tried. England kept picking up the book, but they never got past page one.
And with the significant physical presence of South Africa and Samoa awaiting Wales in New Zealand next month, it augured well for what will be a punishing World Cup pool.
"Our attack wasn't where it needs to be, but the hunger and desperation we showed in defence won us the game," said powerhouse centre Roberts.
"To keep England to zero tries with the threats they've got across the park is quite a feat. Our defence allowed us to do that.
"They broke our line a couple of times, but our work-rate to get back was second to none. At the end of the day, we got the result.
"That is the level we are going to have to be at.
"Come September 11, we play South Africa - a team as physical, if not more physical, than England - and that is the type of performance we are going to have put in, and better it, defensively.
"In terms of our defence, we went up another level, and we will be looking to do that again against Argentina next weekend."
Wales thrived in adversity, restricting England to three Toby Flood penalties despite having two players - Roberts and scrum-half Mike Phillips - sin-binned during a frenzied second period.
They also lost centre Gavin Henson and fly-half Rhys Priestland to injuries, but Wales ultimately kept England try-less, an experience Flood and company had not experienced for 18 months.
And for the second week running, Wales outscored England on tries, backing up a 3-2 verdict at Twickenham last Saturday with full-back James Hook's touchdown sealing a 19-9 Millennium Stadium verdict.
"It's 1-1, I suppose," added Roberts, reflecting on the back-to-back England clashes.
"It was important we won at home, but we haven't won the World Cup or anything. It was a warm-up game, although we were pleased with that performance.
"It's great to feel that result against a good team. It has been a long time coming for us, but we stuck at it.
"We will need to up it again now."
Captain Sam Warburton was at the heart of Wales' watertight defence, underlining his burgeoning reputation - aged just 22 - as a consistent world-class performer.
With hooker and last season's skipper Matthew Rees struggling to overcome a neck injury, the likelihood is that Warburton will lead Wales at the World Cup.
"Everyone had the belief before the game that we would win, it didn't matter who we were playing," Warburton said.
"We deserved better than to lose three times against England in one year. It's definitely my best moment in rugby, leading Wales to victory against England at the Millennium Stadium."
Wales coach Warren Gatland revealed after the game that his players had turned down the opportunity to have a drink in the Twickenham bar following last weekend's 23-19 defeat to England.
And Warburton added: "Wales have obviously had a lot of bad press over the last year with drinking.
"But we made a collective decision that it was best not to drink after the Twickenham game with only the short turnaround of a week.
"We needed to get our recovery in. The best thing was to get back to the hotel and have some good food, bang in the protein shakes and get back to it on Monday.
"We've got a great bunch of boys, and everyone has bust a gut to get this win.
"It was massive with the World Cup around the corner because, as Warren said this week, we have to get into the winning habit."
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