Published: 2019-12-01 21:26:56 BdST
Leonardo Bonucci fired Juve into the lead in the first half, but an exquisite finish from Sassuolo winger Jeremie Boga levelled the scores just three minutes later before Francesco Caputo put the visitors in front after the break following a defensive mix-up and an error by keeper Gianluigi Buffon.
Ronaldo netted from the penalty spot midway through the second half to end his four-match goal drought in all competitions and deny Sassuolo their first ever win in this fixture.
Juventus remain in first place on 36 points, but Inter Milan can move one point ahead of them by beating SPAL later on Sunday.
“We put ourselves in difficulty, we lost our heads in the first half," Juve coach Maurizio Sarri told Sky Italia.
"Every time we lost the ball we were wide open. After going behind we played at a good level for 40 minutes and could have even won the match.
"The games after a Champions League week are always difficult because of a lack of energy.”
The home side were heavy favourites ahead of kickoff, as Sassuolo had failed to pick up a single point in their six previous trips to the Allianz Stadium and the champions had won every home game under Sarri.
Juventus got off to the perfect start when Bonucci drilled a low shot into the bottom corner from outside the box, but the visitors were soon level when Boga dinked a delicate finish past Buffon.
Juve were made to pay for individual errors early in the second half, as Matthijs de Ligt’s clearance fell to Caputo on the edge of the area and the striker’s volley squirmed through Buffon’s body and into the net.
Sassuolo had 18-year-old debutant Stefano Turati to thank for keeping them in front when the goalkeeper acrobatically turned over a dipping Ronaldo free kick, before the Portuguese forward rounded the goalkeeper to score, only to be denied by the offside flag.
Ronaldo had a golden chance to score his first club goal in more than a month when Filippo Romagna tripped Paulo Dybala to concede a penalty, and the 34-year-old made no mistake by blasting a powerful shot into the bottom corner from 12 yards.
Juventus pushed for the winner as Turati made another excellent save from a Dybala shot and Ronaldo flashed a stoppage-time header wide of the target, but Sassuolo held on to end a seven-match losing run against the Turin giants.