The 24-year-old Frenchman, in just his second grand tour, rode away from the day's break with 25km to go and never looked back, finishing just five seconds ahead of the chasing peloton, who swallowed the rest of the leading group with just over one kilometre of the cobbled uphill finish remaining. Sam Bennett (Bora-hansgrohe) was the best of the rest.
“I suffered a lot at the end of the race," the Deceuninck - Quick Step rider said. "The last 25 kilometres were terrible. It was pretty much headwind. I wanted to go faster but I couldn’t. I was afraid they would come back and in the end it worked out. I looked behind in the last straight and I saw they were in the corner.
"Then, I said, ok, they’re too far, I’ve won. Every day we try to do our best with the team. It’s already our fourth stage win. We were riding for Philippe [Gilbert] today. A big group went, I followed and I didn’t have to pull because my leader was at the back. It was my goal, to win a stage at La Vuelta. And this is deliverance."
But it's the Vuelta a España and as usual, nothing went according to plan in the chase behind.
Smashed with rain and intense crosswinds from the outset, a crash at around the 100km mark on a descent brought down Roglic and Astana's Miguel Angel Lopez of Astana.
Roglic and Lopez both came off their bikes, while Roglic’s team mate Tony Martin was forced to abandon due to injuries suffered in the collision.
Movistar, containing second-placed Alejandro Valverde and third overall Nairo Quintana, attacked moments later, much to the annoyance of the peloton. Team Ineos’s Owain Doull told Eurosport: “It depends if they were riding out ahead beforehand - if they weren’t then that was shocking.
“It’s not like they did it for a few kilometres and then sat up, it was pretty divided for a while. If I were Roglic and Jumbo I wouldn’t be happy. I’m not happy and it had nothing to do with me.”
Movistar’s sporting director Jose Luis Arrieta told Spanish television the team had always planned to attack after that descent and accused the UCI of dictating that Roglic and Lopez be allowed to join the main group by moving in the slipstream of team cars, something which is not usually permitted.
After the stage, Roglic insisted he did not notice Movistar putting down the hammer.
Cycling etiquette dictates that if the race leader suffers an accident or mechanical they should be allowed to rejoin the peloton with no attacks permitted, which is where the main bone of contention stems from. Valverde eventually ordered his team to slow down, allowing Roglic to catch up.
Roglic leads Valverde by two minutes and 47 seconds with tomorrow’s 190km mountain stage - containing five climbs - from Arenas de San Pedro to Plataforma de Gredos realistically the world champion’s final chance to claw back time on the Slovenian.
Watch Stage 20 nice and early from 7.50pm AEST streaming at our website and via SBS On Demand and on SBS Viceland from 10.30pm AEST.