LAS VEGAS – Rolando “Rolly” Romero knew the danger involved Saturday night, even if Ismael Barroso looked significantly older than his listed age of 40.

After suffering a third-round knockdown, a sometimes-reluctant Romero fought accordingly over the ensuing six rounds. Romero eventually scored a debatable knockdown of his own early in the ninth round and was awarded a controversial technical-knockout victory in their “Showtime Championship Boxing” main event at The Cosmopolitan of Las Vegas.

Referee Tony Weeks oddly stopped the action at 2:41 of the ninth round.

Barroso was on his feet when Weeks surprisingly stepped between them to halt their scheduled 12-round fight. The Venezuelan veteran appeared to slip most of Romero’s punches prior to the suspect stoppage.

Even Romero admitted that Barroso should have been afforded the opportunity to fight on.

“I’ll be honest,” Romero told Showtime’s Jim Gray, “he’s a warrior and he should have been allowed to continue.”

Nevertheless, the 28-year-old Romero (15-1, 13 KOs) won the vacant WBA super lightweight title in his first fight since Gervonta Davis knocked him out almost a year ago. The left-handed Barroso (24-3-2, 22 KOs) lost by knockout for the third time in his 17-year professional career.

North Las Vegas’ Romero, who went off as a 10-1 favorite, was down on all three scorecards entering the ninth round. Barroso was ahead by three different scores according to judges Tim Cheatham (76-75), David Sutherland (77-74) and Steve Weisfeld (78-73).

“I am fine,” Barroso said. “I think it was an injustice to stop the fight. I was landing the better shots.”

Weeks’ decision baffled Barroso as much as those in attendance and fans who watched on television.

“The referee just stopped the fight and he didn’t say anything,” Barroso said. “You can see it clearly. I’m the one who’s hitting him. There was nothing clear that he hit me with. I don’t understand why they stopped the fight.”

Romero’s left hook hurt Barroso early in the ninth round and led to a knockdown 48 seconds into it. Though Barroso seemed hurt, Romero shoved him to the canvas.

Barroso remained on one knee and gathered himself before beating Weeks’ count.

“It was a push on the [ninth-round] knockdown,” Barroso said. “It wasn’t a big blow or anything.”

Romero and Barroso traded hard shots about 40 seconds into the eighth round. Romero clipped Barroso with a short, left hook on the inside later in the eighth round.

A reluctant Romero mostly kept his distance from the dangerous Barroso during the seventh round. Barroso wasn’t able to land many damaging shots in that round, either.

Barroso blasted Romero with a left hand as Romero fired a right that landed on his shoulder late in the sixth round.

Romero landed a right and Barroso connected with a left simultaneously early in the sixth round, which drew a dramatic reaction from Barroso.

Romero’s right uppercut connected before he pushed Barroso backward with 30 seconds to go in the fifth round. Romero landed a left hook as Barroso came forward with 1:15 to go in the fifth round.

Barroso and Romero exchanged punches near Romero’s corner just before the fourth round ended.

Romero landed a left hook in an exchange with about 1:10 to go in the fourth round. By then, Romero bled from his mouth.

A straight left hand by Barroso knocked Romero to the canvas with just over 20 seconds to go in the third round. Romero reached his feet pretty quickly, easily beat referee Tony Weeks’ count and made it to the end of the round.

Romero seemed more frustrated than hurt when he walked back to his corner.

“I was a little buzzed,” Romero recalled. “I was a little off balance and I got caught. I moved around and got back into it.”

Romero landed a short right on the inside and quickly tied up Barroso with just under a minute to go in the second round. Barroso went down at the midway point of the second round, but only because their legs got tangled.

Romero was careful with Barroso in the opening round. He moved out of Barroso’s punching range when his opponent opened up, but Barroso couldn’t catch him with a clean shot in the opening three minutes.

The fifth-ranked Romero was supposed to challenge Alberto Puello for what was scheduled as Puello’s first 140-pound title defense. Puello (21-0, 10 KOs) tested positive for clomiphene, a banned substance, and was removed from their fight last month.

Critics contended Romero didn’t deserve a title shot because he lost his last fight in a lower weight class and had not competed at the 140-pound limit before Saturday night.

Barroso, who was the WBA’s mandatory challenger in the super lightweight division, replaced Puello, who has since been downgraded to the WBA’s champion in recess. If Puello’s B sample submitted to the Voluntary Anti-Doping Association comes back positive for clomiphene, the WBA is expected to strip the Dominican southpaw of his championship.

Barroso was already training when he stepped in for Puello because he was scheduled to box on the Romero-Puello undercard.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.