Roglic launched an attack on the final climb to Mende just under two kilometres from the finish, opening up a gap on his rivals. While he finished the stage with just eight seconds in hand over Chris Froome, Geraint Thomas (Sky) and Tom Dumoulin (Sunweb), the trio should not underrate the Slovenian.
And Dumoulin does not.
"He was definitely the strongest today," the Dutchman said. "He showed that earlier (this year) in (Itzulia Basque Country) where he also atacked on a steep finish climb.
"He's just really good at those anaerobic efforts. I hope the Pyrenees are going to be more of an aerobic effort and that we will beat him. He wasn't much of an ally today he also took time on me. That's not what I like to see."
While he is still two minutes and 38 seconds behind Thomas, Roglic seems content to chip away while he largely flies under the radar. But he is only 59 seconds behind Froome, and 48 seconds down on Dumoulin.
"Eight seconds is eight seconds," Roglic said in a team video after the stage. "It's OK huh? It's better to win eight seconds than to lose eight seconds. The team did a perfect job they did a great lead out in the end. I went away.
"Every second counts. I have to try a little to see how it goes. You have to try."
Roglic obviously felt good before the stage, joking in the team's video "the beast is there."
"He couldn't resist, our Primoz," team director Nico Verhoeven said in the same video in the team car. "At the moment we're the only team who're giving Team Sky somehwat of a hard time."
Ski jumping under the radar
It's a story repeated often; Roglic was a relative latecomer to the sport after a nine-year ski jumping career and a stint in 2007 as junior world champion. He switched to cycling in 2012 at 22-years-old with Slovenian continental team Adria Mobil, his win at the Tour of Slovenia in 2015 earning him a contract with LottoNL Jumbo the following year.
Like Geraint Thomas, the 28-year-old has not led a team during a grand tour prior to this year's Tour de France. Unlike Thomas, he's only finished two - last year's Tour and the 2016 Giro d'Italia - his first year as a WorldTour professional.
But it was at last year's Tour Roglic foreshadowed his future form. He won the tough Stage 17 to Serre-Chevalier which included two hors categorie climbs. A few months before that, he picked up big ITT wins at the stage races he came back to conquer wholly this year, the Itzulia Basque Country and the Tour de Romandie.
It's this blistering form he carried into the Tour nobody should discount with just the Pyrenees, and a discipline he excels in, the ITT, remaining on the way to Paris.
"He can definitely make it to the podium I am convinced of that," LottoNL Jumbo sports Frans Maasen said.