The 24-year-old arrived at Parc des Princes from Palermo for a reported €39.8 (£34.3m) million in 2011 but has yet to live up to his sizeable price tag following two inconsistent campaigns.
|16/1||PSG are 16/1 with Bet365 to win the Champions League
He told calciomercato.com: "Pastore to Rome? Impossible because PSG have never made him available for sale."
It has been a high-profile summer of activity for les Parisiens, with coach Carlo Ancelotti leaving for Real Madrid after winning the Ligue 1 title and sporting director Leonardo also departing following his 13-month suspension for pushing a referee.
Laurent Blanc has since been installed as Ancelotti's replacement and swiftly made his mark by securing the services of Uruguay striker Edinson Cavani in a €64m (£53.8m) deal.
PSG face Real Madrid in a pre-season friendly in Sweden on Sunday before kicking off their league season against Bordeaux on August 3.