Ranieri, 6 7, was sacked by Fulham eight days ago after winning three of his 17 games in charge.
However, the Roma fan – who handled the club between 2009 and 2011 – was handed a quick return to direction, substituting Eusebio di Francesco.
“When Roma call you, it’s impossible to say no.”
After losing to Porto in the Champions League last 16 di Francesco was sacked on Wednesday.
Roma sporting manager Monchi also abandoned the club earlier on Friday.
1-1 defeats followed including an FA Cup exit at home to League Two side Oldham, although ranieri beat Southampton 32 in his very first game and took over at Fulham last November after the sacking of Slavisa Jokanovic.
He abandoned the Cottagers from safety with 10 games left with all the club 10 points after only 106 days.
Roma president Jim Pallotta said:”We’re thrilled to welcome Claudio Ranieri back to the bar.
“We’ve one aim remaining this season and that’s to finish in the greatest possible league standing and also secure eligibility for the Champions League.”
Roma are three points.
Despite starting the season as 5,000-1 outsiders Leicester was led by ranieri famously to the 20-16 premierleague name.