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 their website: "He can resume full activity after 30 days, barring any complications."
Rocchi did not feature in last night's 3-0 win over Udinese, which took the Biancocelesti within six points of the Serie A summit.
Cristian Ledesma missed a first-half penalty before Alvaro Gonzales, Miroslav Klose and Anderson Hernanes secured victory.
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 Vladimir Petkovic's side and Mauri added: "We are doing very well, the attackers and midfielders are helping out defensively so there are few problems behind.
"We need to improve at set pieces but we are also working to improve this aspect."
Sunday's opponents 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."