Hamilton currently leads his German rival by 59 points in the Drivers’ Championship.
With four races to go, it looks highly unlikely that the Brit will be caught – and Rosberg thinks the title race is already over.
“Ferrari always come back strong,” Rosberg told BBC Sport.
“It’s so difficult for Sebastian now. Lewis has such momentum, everything is going in his direction.
“Sebastian needs a miracle to come back but he’s a fighter and he won’t give up. It will remain interesting so let’s see how far he can take it.”
Meanwhile, Williams are running the rule over over a potential return for Polish driver Robert Kubica, who has not raced since a rally accident in 2011 left him with only partial movement in his right arm.
Rosberg is part of the Kubica’s management team and is hoping to see his driver back soon.
“Williams is evaluating him so we need to be patient,” he said.
“In my 20 years of racing, the fastest guys I saw were Hamilton and Kubica, so I know how fast he can be.
“I am exploring and enjoying this management side of it – it’s different doing it for someone else.
“I was my own manager, but this is another good way to stay connected to the sport.”