The crash came after Roglič attacked 2.6 kilometres from the finish in Tomares, having led a quintet containing eventual stage winner Mads Pedersen (Trek-Segafredo).
Roglič's heavy fall, caused by a coming together with Fred Wright (Bahrain Victorious), allowed Pedersen to power past Pascal Ackermann (UAE Team Emirates) and Danny van Poppel (Bora-Hansgrohe) to secure his second stage win of the race.
It looked to be a successful day for Roglič up until the fall, though he was still able to take time off overall leader Remco Evenepoel (Quick-Step Alpha Vinyl) after being awarded the same time as the other attackers, who finished eight seconds ahead of the bunch.
The defending champion cut a bloodied figure after the finish, with the race doctor's medical bulletin listing "polycontusions and superficial wounds to his right elbow, hip, knee and ribs" among his injuries.
It now leaves some uncertainty surrounding the Slovenian's participation in Stage 17, with further discussions still to be had.
"All investigations for today have been carried out," Jumbo-Visma said on Twitter.
"Tomorrow morning, the team will decide in consultation with the medical doctor whether Primož will continue his fight this @lavuelta."
Despite cutting into Evenepoel's advantage, team sports director Addy Engels said the crash put a bizarre spin on a near-perfect plan.
"Bizarre, I think it’s a good word," Engels said. "We had the plan to try to go for a stage result and, of course, also to take back time on GC with the suitable final. I think that plan went really well.
"Primož got in front with a small group to the finish, but what happened there, we didn’t even know. We had television [in the team car], but we missed the crash itself, so we just thought he finished in the group ahead of the first bunch.
"Then suddenly we hear that he crashed in the last straight. The plan had a very small chance of succeeding on a final like this, but we succeeded. And then it goes all wrong in the last few hundred metres, which is bizarre."
La Vuelta continues tonight with Stage 17 which concludes with a summit finish to Monasterio de Tentuda. Watch from 10:50pm (AEST) on SBS and SBS on Demand for all the action.
