Inter ended a five-match winless streak in Serie A on Monday with a 2-0 win at Chievo, with captain Ranocchia netting the second after Mateo Kovacic had opened the scoring.
That triumph marked Mancini's first in the league since returning for a second stint in charge at Inter last month and Ranocchia has urged his team-mates to build on that performance when they welcome Lazio to San Siro.
"It was important to win at Bentegodi [Chievo's stadium]," he told Corriere dello Sport. "Now we must not stop against Lazio because continuity is critical.
"Mancini is right when he says that it takes a couple of months to learn all his ideas, but we are growing from game to game."
After beating Chievo, Inter sit a disappointing 11th in the Italian top flight and will need to be at their best in order to move into the top half in the final game before the mid-season break.
Mancini won the 1999-2000 Serie A title as a player with Lazio and guided them to a Coppa Italia crown as a coach four years later, and the capital club appear to be in good shape for success in the near future under current boss Stefano Pioli.
Victories over Parma and Atalanta have lifted Lazio to fourth in the table, boosting hopes that they could take Napoli's place in the top three and secure a spot in next season's UEFA Champions League.
Full-back Dusan Basta has outlined European qualification as the goal for Lazio, however, the Serbia international knows the difficulty of taking all three points versus Inter.
"We have the objective of playing in Europe, our next match will be decisive," Basta told Mediaset Premium.
"We expect a very tough couple of games, I feel fine and the team is definitely moving in the right direction.
"We have to continue, with Inter next it won't be easy but we want to win every match."
History is not on Lazio's side, with the visitors possessing a dreadful record in the league against Inter at San Siro.
Lazio's 3-1 away win back in May 2013 represented their first at Inter in Serie A since 1998 and was followed by a return to previous form last season with a 4-1 defeat.
And Pioli will be without a host of players for the encounter.
Midfielder Lucas Biglia has a thigh strain and joins a lengthy injury list that also features Antonio Candreva (thigh) and Edson Braafheid (knee).
Santiago Gentiletti (knee), Ederson and Michael Ciani (both thigh) are all still out, while Inter's only absentee comes in the form of defender Jonathan, who is struggling with a calf problem.
