The chasing pack includes a back-from-injury Chris Froome in his last major race for Team Ineos before the four-time Tour de France winner leaves for Israel Start-Up Nation.
Roglic looked set to win the Tour de France last month until the rider, who will turn 31 later in October, fell apart on a stunning penultimate day, opening the way for fellow Slovenian Tadej Pogacar to take victory.
Since then Roglic has restored some pride by winning the Belgian one-day classic Liege-Bastogne-Liege, profiting from Julian Alaphilippe's premature celebrations to nip past the Frenchman on the line.
Organizers of the Vuelta, the last of cycling's big three tours, have swatted away a series of disruptions from COVID-19.
The planned August start in the Netherlands was switched to October 20 in Spain and then a three-day foray into Portugal was slashed.
In a radical move, the Vuelta has banned the publicity caravan that precedes each stage and spectators will be barred from nine of the mountainsides where the travelling enthusiasts normally gather.
Facial recognition technology will be used instead of pens to reduce the risk of infection. Riders usually register with a signature, needing to use a pen and paper. Instead a computer will analyze the riders' physical characteristics.
Spain is battling one of the highest rates of coronavirus infection in the European Union, with nearly 900,000 infections and more than 33,000 deaths.
The 22 teams of eight riders will not venture further south than Madrid on a gruelling route of 2,882 kilometers that features eight hilly and five mountainous stages.
A long and lonely individual time trial could decide the winner.
Fears the stars would fail to show up have not materialised as Giro d'Italia winners Tom Dumoulin and Richard Carapaz top the roster while climbers such as Spaniard Enric Mas and Frenchman Thibaut Pinot add to the lustre.
Froome's appearance provides interest as he bids to overcome horrible injuries from a high-speed crash last year.
It will give fans the chance to see if the seven-time Grand Tour winner, who was dropped from Ineos' Tour de France lineup this year, is back on top form when two mountainous stages are followed by a draining individual time-trial mid-race. It is the kind of contrasting terrain where Froome, now 35, once so often destroyed his rivals.
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