"The result was massively frustrating but that is the way it goes sometimes and we have to dust ourselves off and focus on the Samoa game," said Roberts.
"Sport can be very cruel at times and losing to the World Champions by one point in the opening game of the World Cup can be a very bitter pill to swallow.
"But we know we need to go out and win our remaining three games.
"The feeling in the changing rooms after was of real disappointment but this tournament is so short we cant dwell on a result like that and there is no doubt that we need to get up in the morning and take the positives from the game.
"In terms of territory we controlled things really well and Rhys (Priestland) showed his maturity and Mike (Phillips) played really well as well.
"From 1 to 15 you couldn't have asked for any more effort it was outstanding, I'm really proud of the performance, but it just wasn't enough in the end."