After missing a spot kick in a Coppa Italia match against AC Milan 10 days ago, Ronaldo made no mistake in the 23rd minute and Paulo Dybala curled in a brilliant second before half-time to give the Turin side a comfortable win.
Juventus, with 66 points from 27 games and chasing a ninth successive title, extended their lead to four points over Lazio, who visit Atalanta on Wednesday. Inter Milan are a further five points behind in third while Bologna are 10th with 34.
Juve's failure to score in two Coppa Italia games following the end of the new coronavirus stoppage, coupled with their defeat on penalties to Napoli in Wednesday's final, raised questions over Sarri, who has struggled to impose his style of play in his first season at the club.
There were no questions about the Juventus defence, however, which kept a fourth straight clean sheet in all competitions.
After fielding Ronaldo in an unfamiliar centre-forward role against Napoli, Sarri returned the Portuguese to his more comfortable position wide of the centre.
Bernardeschi crashed a shot against the crossbar and Ronaldo had another goal disallowed for offside in the second half.