On 7 March, Williams made his debut for the Roosters before a record first round crowd and television audience; he also scored his first try for his new club. On 1 April, Williams scored his second try in the Roosters' 50–0 win over the Eels—their biggest ever victory against Parramatta and the first time they had kept their opposition scoreless in consecutive matches since 1999. On 12 April he scored twice in his first encounter against the Canterbury-Bankstown Bulldogs, with the 38–0 result being the Roosters' largest ever victory over Canterbury. On 5 May he scored his fifth try against the Panthers. On 16 June, Williams scored his sixth try against the Warriors. On 28 July, Williams scored his seventh try against Newcastle, but he was given a two match suspension for a grade three careless high tackle on former Canterbury-Bankstown Bulldogs teammate Willie Mason. On 19 August, after returning from suspension, Williams scored his eighth try against the Wests Tigers. On 6 September he was named man-of-the-match as the Roosters claimed the NRL minor premiership and J. J. Giltinan Shield against the Rabbitohs in front of a record NRL regular season crowd of 59,708. On 6 October, Williams played in the grand final against Manly, with the Roosters claiming the premiership 26–18. Williams later said of the victory "I didn't cry, but it was the first time I've come close to crying." Subsequently, he was awarded the Jack Gibson Medal as the Roosters' player of the year. Several days later he announced that he would continue playing for the Roosters into 2014—the first time he had played consecutive seasons for one team since leaving Toulon in 2010.