The Italian champions took a while to settle into the encounter, their opponents threatening with a dangerous pressing game.
Nine minutes later the hosts had opened the scoring through Miralem Pjanic, whose clean hit from 25 yards out nestled perfectly into the corner of the net.
Midway through the second half, Ronaldo came within a whisker of opening his Juve account as he forced a smart save from Thomas Strakosha with a dipping shot from outside the box.
The Portuguese star then fluffed his lines in the six-yard area by clipping the ball with his heel but Mandzukic was on hand to apply the finishing touch and give Juve an insurmountable lead.
JUVENTUS (4-3-3): Szczesny; Cancelo, Bonucci, Chiellini, Sandro; Khedira (Bentancur 85'), Pjanic (Can 69'), Matuidi; Bernarderschi (Costa 60'), Mandzukic, Ronaldo
LAZIO (3-5-2): Strakosha; Santos, Acerbi, Radu; Marusic, Parolo (Correa 64'), Leiva, Milinkovic-Savic (Durmisi 79'), Lulic; Alberto (Badelj 64'), Immobile