Madrid are aiming to win the tournament for the fourth year in a row and Julen Lopetegui's side cruised to a comfortable Group G victory at the Santiago Bernabeu on Wednesday.
Isco took set-piece duties following the sale of Cristiano Ronaldo to Juventus, and on the same night his former team-mate was sent off against Valencia, the Spain international whipped in a superb strike from 25 yards just before the break.
And Bale, scorer of a brace in Madrid's defeat of Liverpool in last season's final, made sure of the points with a placed finish after racing through on goal from Luka Modric's pass, with substitute Mariano going on to add a third in stoppage time.
Bale had a great chance to open the scoring in the fourth minute, but he rifled wide after collecting an excellent lofted pass from Toni Kroos, then Robin Olsen brilliantly denied Isco.
Kroos and Bale wasted further chances but while Olsen showed off his acrobatics to tip over a Sergio Ramos header he was helpless as Madrid took the lead on the stroke of half-time.
Daniele De Rossi brought down Isco and the Spain star curled a brilliant free-kick into the top-left corner, Olsen seemingly deceived by the strike.
Keylor Navas was selected in goal rather than Thibaut Courtois and he parried away a drive from Cengiz Under, with Bale's deflected shot then bouncing back off the crossbar.
But the Wales star would not be denied again when Modric sent him clear, Bale arrowing a shot home with his trusty left boot.
Substitute Marco Asensio almost added a late third with a delightful no-look finish, but Mariano did wrap up the scoring in the first minute of added time with a fantastic turn and strike into the top-right corner on his first appearance since returning from Lyon.
What does it mean: No Ronaldo, no problem
For much of the first half Madrid missed their talisman as they failed to convert chances, but Isco, Bale and Mariano stepped up to deliver three points for Lopetegui in his first Champions League match in charge. That Ronaldo was dismissed as Juventus won away to Valencia will not have gone unnoticed in Madrid. Roma will still expect to qualify, though, as Viktoria Plzen and CSKA Moscow are ordinary opposition.
Pat on the back: Isco the inspiration
It is fair to say Isco would certainly have not been given the chance to take the free-kick he scored had Ronaldo been on the pitch. But the Spain star justified stepping up with an unstoppable strike that was almost a carbon copy of an effort by Lionel Messi in Barcelona's defeat of PSV on Tuesday.
Boot up the backside: No platform from Dzeko
Starting up front alone was a tough assignment for Edin Dzeko and he did not get a lot of support from the other attackers in the Roma team. But the striker, who had scored in each of his last five appearances in the Champions League, did not hold the ball up for his side, which was surely the minimum expected of him by coach Eusebio Di Francesco.
Key Opta stats:
1 - Isco Alarcon scored his very first direct free-kick goal in the Champions League with his first attempt in the competition. Magic. pic.twitter.com/AFLYN0WS2k— OptaJose (@OptaJose) September 19, 2018
- Roma have lost five of their last seven Champions League games against Real Madrid (2W).
- Roma are winless in their last six Champions League away games (1D 5L), conceding at least two goals per match in that period.
- Roma fired their most shots (13) without scoring a goal in a Champions League match since December 2015 (v Bate Borisov).
- Roma conceded their most shots (30) in a single Champions League game since March 2016 (v Real Madrid).
- Luka Modric has delivered at least an assist in each of last seven Champions League tournaments.
Madrid are at home to Espanyol in LaLiga on Saturday, while Roma are at Bologna on the following day in Serie A. The Italians will hope for a better result when they host Plzen when the Champions League returns, with Madrid heading to Moscow to play CSKA.