Roma have won their last four games to surge level on points with second-placed AC Milan, who ended a difficult week by labouring to a 1-1 home draw with struggling Livorno.
Both sides moved eight points behind leaders Inter Milan, whose match at Parma was postponed because of snow.
New Juventus caretaker coach Alberto Zaccheroni, who replaced the sacked Ciro Ferrara on Friday, got off to a mixed start with a 1-1 home draw against former club Lazio.
Alessandro Del Piero went down under a challenge from Modibo Diakhite and slotted in the 70th-minute penalty before Lazio's Stefano Mauri netted from close range to extend Juve's winless run to five matches.
Juve fans, gave a lukewarm reception to Zaccheroni given he has been out of work for three years and also coached rivals Inter, Milan and Torino.
PERFECT MOMENT
The little-used Okaka was due to make a loan move to Fulham but was named in Sunday's squad because four Roma forwards were out injured, including Francesco Totti and Luca Toni.
The 20-year-old entered the fray on the hour after John Arne Riise's terrific volley put Roma ahead before Simone Vergassola equalised from a tight angle late in the first half.
Okaka then found the perfect moment to score his first league goal this term with a potent backheel from eight metres.
"I told him 'you're not leaving now'. He fainted," Ranieri joked to Sky TV, hinting Okaka would still go to Fulham.
Milan could have done with a moment of magic after another lacklustre San Siro display following last Sunday's defeat by nine-man Inter and Wednesday's Italian Cup exit against Udinese.
Before kick-off, chief executive Adriano Galliani declined to deny reports of a swap between Milan left back Marek Jankulovski and Inter winger Mancini on Monday's transfer deadline day.
Ronaldinho struck a post before David Beckham swung in a cross and Massimo Ambrosini hooked home a minute from the break.
Livorno, whose coach Serse Cosmi resigned last week before changing his mind, deservedly equalised on 53 minutes when Cristiano Lucarelli prodded in Claudio Bellucci's scuffed shot.
A bad week for Fiorentina also ended on a dull note with a 2-2 draw at Cagliari which left the Florence club 11th.
Striker Adrian Mutu has been suspended for testing positive for a banned appetite suppressant and Fiorentina's bid to sign Antonio Cassano from Sampdoria as his replacement fell through.
Cassano was injured but Samp still sealed their second straight win after a bad spell with a 2-0 victory over Atalanta.
Catania drew 1-1 with Udinese and Bologna 1-1 at Chievo.
