The 65-year-old coach was dismissed after a 4-2 home loss to Cagliari proved to be the final straw for the club's directors.
The result saw the Giallorossi drop to eighth in the league having been unable to register a win in any of their past five league matches.
Pjanic believes the decision would not have been an easy one for the club, and hopes that Roma's fans can get behind the team as they look to move forward under caretaker boss Aurelio Andreazzoli.
“It was certainly not an easy decision for our directors to make,” Pjanic wrote on his Facebook page.
“I am so sorry it ended this way and I wish the coach all the best. Now we must turn over a new leaf and I ask all of you to be united so we can bring normality back and emerge from this situation for the good of our Roma!”Andreazzoli's first game in charge will be away at Sampdoria next Sunday.