The 35-year-old fractured the fifth metacarpal of his right hand in training and immediately had a plaster cast applied.
The club confirmed in a statement on its website: "He can resume full activity after 30 days, barring any complications."
Rocchi did not feature in the midweek 3-0 win over Udinese, which took the Biancocelesti within six points of the Serie A summit.
Midfielder Stefano Mauri told the Lazio Style Channel: "Udinese wilted a little in front of us and we took advantage to earn an important victory."
The game also brought a third successive clean sheet for
"We need to improve at set pieces but we are also working to improve this aspect."
This weekend's opponent Parma will also go into the game in high spirits after beating Inter Milan 1-0 and Mauri admitted: "They're a good team and it will not be easy.
"But we have demonstrated the ability to beat anybody, so we have to try to impose our game. Sometimes, unfortunately, we do not and we suffer. We need to improve from this point of view."
Inter Milan president Massimo Moratti has refused to rule out sending striker Antonio Cassano to Parma as part of a swap deal for Ishak Belfodil.