The Slovenian, one of the race favourites after winning all three races he has entered this season, clocked 12 minutes 54 seconds over eight kilometres from Bologna to the top of the San Luca hill.
"I'm in very good condition and am very satisfied by my performance and by the time I gained over my opponents," the 29-year-old Roglic, a former world junior ski jump champion, told reporters.
He beat Briton Simon Yates by 19 seconds after the Mitchelton-Scott rider, who had warned that his rivals should be scared of him, looked impressive in the final two kilometre climb.
Home favourite Vincenzo Nibali was third, 23 seconds off the pace as the Team Bahrain leader got off to a decent start in his quest for a third Giro title after triumphing in 2013 and 2016.
Dutchman Tom Dumoulin, a time trial specialist, was left disappointed to finish fifth, 28 seconds behind Team Jumbo-Visma's Roglic and on par with fourth-placed Miguel Angel Lopez, of Colombia.
"I thought I had managed my effort well," said Dumoulin, who had no indication of his opponents' form after being the first rider to go down the starting ramp.
"I don't understand why it did not work. It's not a good start to the Giro."
Yates, who last year looked set to win the race when he crumbled on the last mountain stage, decided to depart among the last starters despite possible rainfalls and the choice paid off.
After a slow start, the Vuelta champion produced a massive effort in the tifosi-packed climb up San Luca.
"It was the tactic, I could not go full gas all the way," said Yates.
"There's not been a gap between the main favourites, expect for Roglic, which everyone was kind of expecting, really."
Team Ineos's Tao Geoghegan Hart finished a promising seventh, 35 seconds off the pace.
"I felt so, so good and then all of a sudden the devil came and hit me with a big hammer," said the highly-promising 24-year-old Briton, who is making his Giro debut after winning two stages in the Tour of the Alps last month.
Sunday's second stage is a mostly flat 205-km ride from Bologna to Fucecchio.
(Reporting by Julien Pretot; Editing by Ian Chadband)
Share
