With just six rounds of the Serie A season remaining, the Bianconeri have an eight-point lead over the Giallorossi, who have been rocked by the news that in-form forward Mattia Destro will miss four games through suspension.
However, the Bianconeri general manager has no doubt that Rudi Garcia's men will still be able to maintain their surprise title challenge.
"Destro is a little champion, but Roma can do without him, as they are a great team," Marotta told reporters. "The club is highly motivated, play well together and can cover for his absence.
"We have a good lead at the top, consolidated with an extraordinary campaign, but there are still 18 points to go and the Scudetto race isn’t over yet."
Marotta also stressed that being the dominant team in Italy has not been easy for Juve.
"For three seasons we have been the pace-setters and this puts a lot of strain on a side," he explained.
"But thanks to [coach] Antonio Conte we have maintained our position at the top and will try to stay there for even longer."
Juve's success this season has been founded on the sensational goalscoring form of summer signings Carlo Tevez and Fernando Llorente and Marotta finds it extraordinary that neither the Argentine nor his Spanish accomplice are likely to travel to Brazil with their respective nations.
"Carlos Tevez and Fernando Llorente have scored 31 goals between them and I think they both deserve to go to the World Cup," he stated.