The 24-year-old, who moved to Madrid form Manchester for a world record fee of £80 million ($132.2 million), wore the famous number 9 shirt for the first time as he started on the right for the Spanish team.
The normal capacity for the ground is 3,300, but three temporary stands erected specifically for this game bumped the capacity up to 11,000, which provided the Irish team with a decent gate on the night.
Ronaldo, who was booed as he made his first touches early in the game, had a relatively quiet night. The Portuguese winger had two free kicks to try and open his account for the nine-time European Champions, but one was blocked and the other went wide.
The former Manchester United star also had a shot from distance trickle wide, but still showed signs of the pace, flicks and dribbling that have made him a star around the world.
Shamrock Rovers defended with gusto and their mid-season fitness stood to them as they took on the galacticos from Spain, who looked like a team playing its first pre-season game.
Rovers’ keeper made some decent saves and the defense in front of him stood strong in the opening period. The second half saw a plethora of changes, most notably the exit of Ronaldo and the introduction of new French striker Karim Benzema.
Though the tempo slowed down in the second period, Rovers withstood everything their illustrious opponents threw at them, and could have gone ahead had Dessie Baker not fluffed a great chance in the 75th minute after some terrible defending from the Spanish.
However, Benzema made Baker and Rovers pay for that miss in the 86th minute when he took down a long ball from Gabriel Heinze and calmly dispatched in to the net to open the scoring and break Hoops fans' hearts.