An early Mario Mandzukic goal and a second-half strike from Blaise Matuidi gave Juve its third win in as many league games this season, although Ronaldo was left without a goal in his first 270 minutes with the Turin side, Reuters reported.
Ivorian forward Gervinho scored in between for Parma, his first goal since joining Parma in the close season.
Earlier on Saturday, Inter Milan midfielder Radja Nainggolan scored on his injury-delayed debut to set Nerazzurri on the way to their first win of the season as they beat Bologna 3-0 away.
Antonio Candreva, with his first Serie A goal since April last year, and Croatia World Cup forward Ivan Perisic added two more goals in the last 10 minutes as Inter cantered home, finally beginning to look like a title contender.
“(Ronaldo) has to deal with different difficulties in Serie A but he had a good game overall,” said Juventus coach Massimiliano Allegri.
“The international break will make him sharper.
“He’s the world’s best player, he wants to score at all costs but he needs to remain calm and the goals will come in a burst.”