But he has returned to action this season and jetted to Spala for the Six Nations champions' boot camp ahead of their autumn series matches against Argentina, Samoa, New Zealand and the Wallabies.
"The way things panned out for Wales on tour is motivation enough in itself for all of us as we go into a tough campaign this autumn," said Roberts.
"We are back out in Poland and putting in all the hard work necessary to ensure we are best placed to achieve our aims this November.
"I've been out here on both occasions previously and those camps were followed by a World Cup semi-final and a Six Nations Grand Slam, so there is no reason why we can't achieve similar levels of success this autumn."
Roberts has struggled to find his top form since returning to action and was part of the Blues' side humiliated 59-22 by Leinster last weekend.
But he remains happy with his progress and reckons he is slowly getting back to his best.
"It's good to be back fit again and good to be back with Wales," added Roberts.
"I have had three or four full games back now with the Blues, we may have had some disappointing results but I feel as though I'm getting back into the groove and becoming battle hardened again.
"All players want to play and it was particularly difficult place for me to be this summer, watching Wales play out in Australia and come so close."