The Belgium international has long been linked with a move to Chelsea, while a number of Chinese Super League clubs - including Beijing Guoan - have been credited with an interest.
Nainggolan's current deal with Roma will run until the summer of 2021, but he has revealed that he would be open to 'signing for life' in Rome.
"I am very happy here and I don't see any reasons why I would want to leave," he told Sky Sport Italia. "I am living well and I have everything that I need.
"I might sign here for life since I have rejected many teams in the past. If the team decides to sell me in the future then I can't do much but at the moment, I am very happy to be here in Rome."
The 29-year-old joined Roma from Cagliari in the summer of 2014, and managed 14 goals for the Italian giants last season.