Sent off against Valencia in midweek, the Portugal superstar gained a measure of redemption by sweeping home from close-range before substitute Federico Bernardeschi netted in stoppage time to maintain the champions' perfect start in Serie A.
It had looked as though Ronaldo would endure a no less frustrating affair than on his return to Spain, as he failed to convert a succession of chances against the promoted hosts.
But a heavy deflection from Miralem Pjanic's initial attempt dropped kindly for the 33-year-old to exorcise his demons and Bernardeschi was on hand to crown a well-constructed counter attack.
Reduced to tears on Wednesday, Ronaldo's mood was hardly helped in a scoreless opening 45 minutes at Stadio Benito Stirpe.
Marco Capuano hooked his poacher's effort off the line in the seventh minute and a second attempt soon after drew a sharp near-post save from Marco Sportiello.
Irritation turned to angst when he sliced over the bar just prior to the hour before Sportiello, on loan from Atalanta, added to Frosinone's increasing hope of a famous result.
The goalkeeper bravely dived at Ronaldo's feet to smother an inventive backheel in a sign of the hosts' commitment to escaping with a point.
In the end, though, there was to be no denying Juve's main man.
He finally broke the deadlock in the 81st minute and provided a key pass in the lead-up to Bernardeschi's breakaway second, the substitute picking out the bottom corner to make safe Juve's three-point buffer atop Serie A.
What it means: Bianconeri battle to the end
Just as they did on the way to overcoming Chievo on the opening weekend, Juve demonstrated patience in unpicking a lesser opponent.
Remaining dangerous until the death is a precious skill that makes an eighth consecutive Scudetto seem almost assured.
This was a test of character for Ronaldo and he once more proved to be of tough mental fibre.
It would have been easy for the forward to fade out of the contest after a string of lost opportunities but, even at the end of a testing week, he maintained concentration to play a decisive role.
Cuadrado fails to deliver
Allegri clearly anticipated Frosinone's negating tactics as he stationed Juan Cuadrado at right-back with a licence to attack.
What the Bianconeri boss did not expect was consistently poor delivery from the natural winger, who, like many of his team-mates, was generally unable to hit the target with crossing opportunities prior to his 69th-minute removal.
Key Opta facts
- Frosinone have failed to score in each of their first five Serie A games – the first time a team has experienced such a drought since Venezia in 1998-99 campaign.
- Juventus' 30 shots are their most in a Serie A game since hitting the same number against Chievo in January 2016.
- Ronaldo has attempted 8.4 shots per game on average in Serie A, more than any other player in the competition since 2004-05. He has now launched 42 efforts at goal – four more than Frosinone's overall total.
- Five of the six goals scored by Bernardeschi in Serie A have come away from home.