The 42-year-old Argentinian, who won the Italian title in 1994, had the penalty imposed when his playing partner reported that he had grounded his putter on his line during a practice putt. Romero made up the strokes and picked up another for good measure as he scored a three-under-par 69 to move to seven-under-par on 137 and into a one-shot lead.
Sweden's Patrik Sjoland, who ran up a triple-bogey after another curious penalty incident, and Britain's Gordon J Brand and Brian Davis were Romero's closest pursuers. Ian Woosnam's 73 took him to 140.
The previous day's events unsettled Romero, but he still picked up three birdies. In two rounds he has collected nine birdies without dropping any strokes other than his penalty.
"I was worried I might not be able to get the penalty out of my mind," he said. "I trusted my playing partner [Carl Mason], who reported that I had touched the line of my putt, even though I couldn't remember doing it. I just had to try to forget it."
Sjoland's triple-bogey came at the sixth on his way to a 70, which also included an eagle and five birdies. While searching for his ball with his partner, Nicolas Vanhootegem of Belgium, Sjoland saw it drop to the ground out of a bush.
When it could not be determined who had disturbed the ball, officials had no option but to penalise Sjoland one stroke. The Swede then added another because his ball had landed in an unplayable lie.Reuse content