Rosberg currently holds a 19 point adcantage going into the final two rounds of the season, meaning that if he wins the Brazilian Grand Prix this weekend, he will be crowned world champion.
"For the moment, things are going well for Rosberg," Villeneuve told www.Minute-Auto.fr.
"He is driving with a lot of maturity and reflection, even if he has lacked speed in the last two races.
"Hamilton has returned to his previous level of concentration but both drivers have had difficult periods and Rosberg is the more responsive," the French Canadian added.
"I feel that he is progressing every season, unlike Hamilton who relies on his natural talent alone."
However, he said that despite Lewis Hamilton's poor reliability record, Rosberg - who has had his own struggles in the past - could suffer his own problems in the final two races.
"No, because Nico also had glitches," he said.
"It (his success) is that throughout the season, he was focused on every grand prix and if he wins the championship, it would have been the little things that allowed him to do it.
"But nothing is decided," Villeneuve said. "A small problem for Rosberg and Hamilton can leave Brazil leading the world championship. So it's not over."
Bahrain International Circuit - Winter testing