Maurizio Sarri showed up with two changes from the side that went down 2-1 to Napoli last weekend, as Adrien Rabiot replaced Blaise Matuidi and Douglas Costa shifted in for Paulo Dybala.
Fiorentina started strongly after Federico Chiesa set up Erick Pulgar for a strike on goal inside eight minutes, but Juventus shot-stopper Wojciech Szczesny got down to gather the effort.
Szczesny made another superb save on 23 minutes this time to deny Chiesa, who flicked a dangerously looking cross towards the far corner with Juve on the edge.
Juve hit the front though five minutes to halftime when Ronaldo tucked home from the penalty spot after German Pezzella handled in the area, after a check from the Video Assistant Referee.
That was the Portuguese superstar's ninth successive goal for the Old Lady, becoming the first player to do so since David Trezeguet in the 2004/05 campaign.
Fiorentina looked for a positive start straight after halftime and turned to bench 12 minutes in to bring on Dusan Vlahovic who came on for Rachid Ghezzal.
Gonzalo Higuain went close to doubling his side's lead on 64 minutes, but Bartlomiej Dragowski's sharp reflexes kept the Argentine's at bay. That was the veteran forward's last play of the day and was soon replaced by Dybala four minutes thereafter.
Juve were given a second penalty in the final 12 minutes when Federico Bernardeschi went down under challenge from Federico Ceccherini and Ronaldo stepped forward yet again to notch home. With that goal, Ronaldo has now scored 50 goals for Turin outfit.
The champions completed the victory when Matthijs De Ligt headed home a pinpoint delivery from Dybala in added time to send his side six points clear at the top of the table.