Rousillon was a dark bay or brown horse with no white markings[2] bred in Kentucky by W. L. Jones and William Stamps Farish III.
At the time, Harwood was noted for his modern approach to training, introducing Britain to features such as artificial gallops and barn-style stabling.
In September he was moved up in distance for the Westhampnett Stakes over one mile at Goodwood Racecourse and won again, "trouncing" a strong field which included the future Melbourne Cup winner At Talaq.
He took the lead in the straight and looked likely to win easily, but appeared to "go to pieces" in the final furlong and was beaten two lengths by Gold and Ivory.
In the Irish 2,000 Guineas at the Curragh in May he started second favourite, but after moving forward in the straight he failed to persevere with his effort and finished fifth behind Sadler's Wells.
In a rough and controversial race, Rousillon finished second by half a length to Chief Singer but was disqualified and placed last for causing interference to the winner in the closing stages.
He started the 8/13 favourite and won by half a length from Prego although Starkey appeared unwilling to use his whip on the winner, who seemed reluctant to continue his run after taking the lead.
He took the lead in the straight and looked likely to win easily but slowed abruptly and veered to the left in the closing stages, finishing third behind Procida and Nikos.
Ridden as usual by Starkey, he took the lead inside the final furlong and accelerated clear to win by two and a half lengths from Celestial Bounty.
Timeform described the race as a disaster for Rousillon: he walked out of the starting stalls and had to be hard ridden by Starkey to make up the lost ground.