[1] Roberts' proposal to create a rival motorcycle championship in 1979 broke the Fédération Internationale de Motocyclisme (FIM) hegemony and increased the political clout of Grand Prix racers, which subsequently led to improved safety standards and a new era of professionalism in the sport.

[6] As a child growing up in the rural agriculture area just off highway 132 near the West side vineyards of E & J Gallo Winery, Roberts was originally interested in horseback riding.

[12] Carruthers ended his riding career after the 1973 season to concentrate full-time on maintaining and tuning Roberts' motorcycles while mentoring him in the AMA Grand National Championship, while Doyle remained as his business manager.

[15] Roberts made a name for himself that year by battling the dominant Harley-Davidson factory dirt track team aboard an underpowered Yamaha XS650 motorcycle, making up for his lack of horsepower with sheer determination.

Despite his Yamaha dirt track motorcycle lacking the horsepower of the Harley-Davidson team, he won three races and consistently finished among the top ten, amassing a record 2,014 points in the 25-race series.

In the 1974 Daytona 200, after early leader Gary Nixon retired, Roberts battled for the lead with former 500 cc world champion, Giacomo Agostini before an overheated engine forced him to settle for second place.

[20][21] Although Roberts finished second to Agostini once again, his first European racing experience left a deep impression on him as, he marveled at the size of crowds and the warmth of the Italian fans.

The Transatlantic Trophy match races pitted the best British riders against the top American road racers on 750cc motorcycles in a six-race series in England.

In a desperate effort to keep Scott within reach in the points chase, Roberts and Carruthers built a dirt track frame to house a 170 mph Yamaha TZ750 two-stroke road racing engine.

[32] As Roberts learned to control his horsepower advantage, he began to work his way from last place through the field as his two stroke motorcycle emitted a high pitched wail throughout the venue that energized the spectators into a frenzy as they watched his progress.

[32] In order to maintain speed, he was forced to ride along the outer edge of the race track, often having his foot peg clipping the hay bales placed around the circuit perimeter as a safety measure.

[31] Although Roberts won four Grand Nationals in 1976, he continued to experience mechanical misfortunes as well as a horsepower deficit to the Harley-Davidson motorcycles in the mile and half-mile dirt track events.

[38] Roberts then travelled to Italy where he raced in the Imola 200, leaving no doubt he was capable of competing at the international level by winning both legs and setting a new track record.

[1] The resulting tire spin caused the motorcycle to buck and shake as it continually lost then regained traction, creating a brutal, violent riding style that no one had ever seen before on the racetracks of Europe.

[50] The thought that race organizers feigned having no knowledge of the Yamaha factory sponsored American champion incensed Roberts, who felt that the FIM was trying to exert their authority on the newcomer.

[48][50] Roberts then won his first-ever 500 cc Grand Prix with a win in Austria, quickly followed by two more victories in France and Italy, along with two second-place finishes in the Netherlands and Belgium.

[54][55] The final race of the season was the German Grand Prix held at the daunting, 14.2 miles (22.9 km) long Nürburgring racetrack, considered too dangerous for the Formula One championship.

[64] His crew managed to replace the seal in time, but Roberts went to the starting line with his gloves coated with oil, causing his hand to slip on the throttle during the race.

The event featured numerous lead changes throughout the 28 lap race, with Roberts winning ahead of Sheene by a narrow margin of just three-tenths of a second.

[68][69] When Roberts first arrived on the Grand Prix scene, motorcycle racers were competing in front of tens of thousands of paying spectators for as little prize money as $200, at venues such as the Imatra Circuit in Finland that featured railroad crossings and hay bales wrapped around telephone poles.

[71] Roberts adopted a confrontational, sometimes belligerent stance with race promoters, challenging the previously accepted poor treatment that motorcycle racers of the day were accustomed to receiving.

[1] Faced with the possibility of losing their grip on the world championship, the FIM was forced to take their demands seriously by making changes regarding rider compensation and safety.

[1][4] During the 1979 FIM Congress, new rules were passed substantially increasing prize money by as much as 500%, and in subsequent years stricter safety regulations were imposed on race organizers.

After more than a year away from dirt track competitions, Roberts won the Houston TT race to tie Bart Markel's career record of 28 Grand National victories.

[76] He then narrowly lost the British Grand Prix to Jack Middelburg by three-tenths of a second before ending his season with a seventh place in Finland and a retirement in Sweden.

[1] Roberts then won the Spanish Grand Prix at Jarama ahead of Sheene, and scored a second place behind Suzuki rider Franco Uncini in the Dutch TT.

[1] Yamaha team manager Giacomo Agostini had been unable to agree on a contract with rider Graeme Crosby, so AMA Superbike champion Eddie Lawson was brought in as Roberts' new teammate.

[1] The 1983 battle for the championship between Roberts and Honda's Spencer would be considered one of the greatest seasons in motorcycle Grand Prix history, along with the 1967 500 cc duel between Mike Hailwood and Giacomo Agostini.

[82] In a fitting end to a great career, Roberts won his last-ever Grand Prix race, however Spencer was able to secure second place to claim the world championship.

[86] In September 1985, he appeared at the Springfield Mile Grand National dirt track race riding a Mert Lawwill-prepared Harley-Davidson XR750, but failed to make the final.