Juve conceded a last-gasp goal to Lazio last time out to make it only three wins from seven league outings this term, but Ronaldo inspired it to three points on Sunday (AEDT) by scoring for the fifth straight league game.
The Portugal international curled in the opening goal with 38 minutes played and grabbed a second with an impressive hooked finish shortly before the interval.
Andrea Pirlo's side was unable to add to its tally but Ronaldo's brace was enough as it moved into second place, albeit having played a game more than the majority of the teams around it.
Federico Bernardeschi rounded off a flowing team move with a thumping finish after 11 minutes but the goal was ruled out because of Alvaro Morata being offside in the build-up.
The lively Bernardeschi had a shot saved by Alessio Cragno and Dejan Kulusevski fired wide from a good position before Ronaldo cut to his right and picked out the far corner.
Ronaldo did not have to wait long for his second, sticking out a leg to send Merih Demiral's flick-on flying past Cragno from eight yards with an improvised finish.
Having played an important part in that second goal, Demiral nearly added Juve's third as his powerful header cannoned off the crossbar.
Cragno kept out another attempt from Bernardeschi three minutes later and the missed chances nearly came back to haunt the home side.
Ragnar Klavan nodded into the bottom corner with a little over 20 minutes left but the goal was chalked off for a foul on returning Juve defender Matthijs de Ligt.