He is a two-time medalist at the World Championships (one gold, one silver), and represented Australia at the 2012 Summer Olympics.

At the 2011 World Aquatics Championships, Roberts won a total of two medals, one gold and one silver.

In the 100-metre freestyle final, Roberts recorded a personal best of 47.63 seconds, finishing behind James Magnussen who won in 47.10.

In his first event at the 2012 Summer Olympics in London, the 4×100-metre freestyle relay, Roberts swam the anchor leg in a time of 48.09.

The Australian team, although the favorites, failed to medal and placed fourth in the final with a time of 3:11.63.