The 26-year-old had previously been fined for hitting the 20-year-old Argentine during the Giallorossi's 2-0 defeat to Udinese last year.
Osvaldo, who netted Roma's only goal against Juve from the spot, said that allegations of another altercation are "not true".
Osvaldo posted: "Enough of this story I had a fight with Lamela. It is not true!"
The Argentine-born Italy international was fined £40,000 for hitting Lamela last season.