Riccardo Saponara thought he had given Sampdoria a point when he curled a delightful shot past Mattia Perin and was booked for throwing off his shirt as he celebrated, Reuters reported.
But, after a delay of nearly three minutes, referee Paolo Valeri ruled that there had been an offside in the buildup.
Leader Juve reached the season’s halfway-mark with 53 points out of a possible 57, a Serie A record for a 20-team championship.
Ronaldo gave Juventus the lead after two minutes, collecting Paulo Dybala’s pass and cutting inside to score with a low shot.
Fabio Quagliarella levelled in the 33rd minute, scoring for the ninth league game in a row when he converted a penalty awarded after a VAR review when the ball hit the back of Emre Can’s outstretched arm as he jumped for it.
Juve’s winner also came for a handball although the ball only brushed Alex Ferrari’s arm which did not appear to be outstretched.
The referee immediately pointed to the spot but Ronaldo had to wait more than two minutes to take his kick while the incident was reviewed on the pitchside monitor.
The Portugal forward took his tally to 14 goals, making him Serie A’s top scorer.