With only 10 Welsh starts to his name prior to departure for the Republic, Roberts travelled to South Africa as one of the less-heralded players in Ian McGeechan's squad but he soon made an impact on the world stage.
Roberts impressed against the Royal XV, Golden Lions and the Sharks before earning himself a Test place at inside centre alongside Lions legend Brian O'Driscoll.
In the first Test against the Springboks in Durban, Roberts was a constant threat. His power and physicality regularly took the Lions over the gain line, while his ability to offload in the tackle created the Lions' first try for Tom Croft.
And while the tourists lost both the first and second internationals and injury forced Roberts to miss the final Test win Johannesburg, the Cardiff Blues star finished the tour with a far greater reputation than when he was first announced as a 2009 Lions tourist. Not a bad achievement for a young man whose immediate goal had simply been to become a permanent fixture in his regional set up in the Welsh capital.
"It's been meteoric and pretty crazy, really," Roberts told Red Bulletin magazine.
"As a young player in your first couple of pro seasons, you're just hoping that you establish yourself in a club team and take it from there.
"But it has all come so soon for me. It's nuts to think there are guys in their late 20s and 30s who are reaching the pinnacle of their career, which is the Lions Test shirt, and I had it at the age of 22. It brings a huge responsibility, but you take it in your stride, and prepare to be a marked man!"
And while others have sung his praises for his stunning contribution as a Lion, Roberts takes a far more modest and understated view of the journey he took to wear that coveted red shirt.
The Welsh speaker points to lady luck and a large slice of fortune when explaining how he became Britain and Ireland's first choice No12 - an achievement that he still struggles to get his head around even now the 10-match tour is a thing of the past.
"The Lions is something you never forget," added Roberts.
"I was picked for the first tour match, against the Royal XV, and there was a plaque in the changing room before the start, listing the names of players who'd played in my position before for The Lions - Jeremy Guscott, Will Greenwood - real legends of the game. And that's when it hit home how big it is, and how much of an honour and a privilege it is.
"You need luck to get on a Lions tour in the first place, and then there's form on tour. For example, Riki Flutey was injured early on and maybe didn't get as good a chance as he wanted to.
"It's about taking a chance when you get it. That's how the big stars make their names - performing on the big stage - and hopefully I'm one step closer to that."