Evenepoel shows his 'good legs' and clean heels to Roglic
When Evenepoel, a Belgian who rides for Soudal-Quick Step, surged away from the pack with a few hundred metres (yards) to go, only Roglic, of Jumbo-Visma, was able to respond.
Evenepoel pulled clear on a final uphill bend to win by two seconds at the end of a mountainous 180.6km ride from Olost.
"I had super good legs," he told broadcaster Eurosport. "I really felt I was getting better and better and better every day."
Evenepoel claimed a 10-second victory bonus, while Roglic gained six seconds for finishing second. That left the two men tied on 12 hours 42 minutes and 17 seconds.
Roglic kept the leader's jersey. He has two second places and a win in the three stages. Evenepoel had a third and a second before Wednesday's win.
"I show already for a few days I'm pretty fast," said Evenepoel, who was wearing the white jersey of the best young rider in the race rather than his rainbow jersey as world champion.
"It's a pity I have the young jersey because I would like to have victory in the rainbow with my memories."
He said his Soudal team had set out to put pressure on their rivals from the penultimate climb, to 1,890m on Col de La Creueta, which race organisers ranked as harder than the finish.
"We saw the climb before La Molina was a tough one and a long one and we went close to 2,000m," he said. "We wanted to make it as hard as possible from that climb on. It paid off."
Giulio Ciccone led the pack home and remains third at 19 seconds. Mikel Landa and Joao Almeida are next, already 44 seconds behind the two leaders.
"They were just on another level today," said Almeida. "I think nobody could follow. Everyone was just playing for third place."
The race is serving as an appetiser for the Giro d'Italia, starting on May 6.
While Thursday's 188.2km stage from Llivia to Sabadell gets its one big climb out of the way early and then heads steadily downhill, stage five on Friday ends with a ferocious climb up Lo Port, a cliff-girded hill just outside Barcelona.
"Expect a nice battle," said Evenepoel. "We should save our energy tomorrow."
On another bad day for Ineos, former Tour de France winners Egan Bernal and Geraint Thomas were again dropped and finished more than 10 minutes adrift.