In 1926 Roberts joined the Auckland Model Engineering Society and began building his first garden railway. Using 1¾ inch gauge track, Roberts, his brother George and W. W. Stewart built a large railway (known as the "RSR Railway") over the next 50 years at Roberts home in Epsom, Auckland. Roberts built his models from then on to a scale of 1:24 (G scale). His meticulously accurate working models of examples of the locomotives and rolling stock found on New Zealand railways became a local attraction. The popularity of this layout led to Roberts being commissioned in 1938 by NZR to build and operate a working model train layout for the New Zealand Centennial Exhibition.