The Serbia international was left in awe of his team-mate, who danced his way through the Rossoneri defence before opening the scoring at the Stadio Olimpico with a cool finish
With Juventus on the verge of another title, Rudi Garcia's men had to pick up maximum points to prevent the Turin giants potentially claiming the crown on Monday night, and the Bosnian's fine solo goal combined with Gervinho's second-half strike to secure maximum points for the capital side.
And Ljajic paid tribute to his colleague for making a vital breakthrough, with Pjanic jinking his way past two players as he danced his way straight through the heart of the Milan defence before coolly sliding the ball past Christian Abbiati.
"In the first 15 minutes, we didn't play well but then we raised our rhythm and Pjanic scored a goal the likes of which you only see once in your life," he enthused. "After the break, we played our game and the victory arrived like this.
"We're not going to give up until the end but it doesn't depend solely on us. We're waiting for Juventus here [on May 9]. We can win against anyone."
Meanwhile, Ljajic revealed that he wants to remain at Roma "for a long time" but says that his future will only be decided at the end of the season.
The Serbia international only joined the Giallorossi from Fiorentina for an initial €11 million last summer but he has failed to nail down a regular starting berth in Rudi Garcia's team, and Viola boss Vincenzo Montella admitted last week that he would welcome the 22-year-old back at the Artemio Franchi with open arms.
However, while Ljajic freely admits the he does not know what the future holds for him, he is hoping that he will still be at the Stadio Olimpico next season.
"I hope to stay at Roma for a long time," the attacker told Sky Sport Italia. "I like this city and I like playing in this team.
"We'll see at the end of the season what the club decide. We'll speak again when the championship's finished."