The hosts saw two chances to take the lead go begging before the 10-minute mark, with Bale firing a low strike just wide of the goal and Isco being stuffed on the doorstep by Robin Olsen after Luka Modric sprang him in the Roma penalty area.
The night was meant to be all about Ronaldo's first Champions League appearance for the club he has tormented so often down the years for Real Madrid.
But Juventus, who had totally dominated until Ronaldo's dismissal, were awarded two penalties within six minutes either side of half-time, and Miralem Pjanic confidently dispatched them both. "Real Madrid are one of the best teams in the world and they have a great squad but it's obvious the departure of Ronaldo makes them less strong while Juve have become a clear favourite for the Champions League", he said.
The Wales worldwide also has four Champions League winner's medals to his name. Its next Champions League match is at home against Young Boys, which Massimiliano Allegri's squad should have no trouble handling in Turin.
Cristiano Ronaldo enjoyed great success at Manchester United
"Obviously it helps", said Bale.
But English champions Manchester City struggled, with Pep Guardiola watching from the stands after a touchline ban, and were beaten 2-1 by French side Lyon at the Etihad Stadium after an error-strewn display. "We conceded many counter-attacks and at this level you get punished", said City assistant coach Mikel Arteta, who was filling in for Guardiola.
Meanwhile, in group G, the defending European champions, Real Madrid, will lock horns with AS Roma, and Viktoria Plzen of the Czech Republic will host CSKA Moscow. There had been no sense of a panic for a team that won its opening three games without Ronaldo scoring, yet a quiet sense of insecurity did linger.
Bayern Munich beat Benfica 2-0.