Rocca collected six birdies, including three straight starting at the 13th, to get to 9-under-par 201 at Lyon Golf Club's Sangliers course on Sunday. The 44-year-old Italian posted his breakthrough victory at Lyon's Brocards course in the 1993 Open V33 Du Grand Lyon. Later that same year he won the French Open in a playoff.
Rocca and the rest of the field head right back out to play the final round, as persistent rains this week have caused numerous delays and necessitated a 36-hole final day.
'I played well, holed some putts and if I can hole some more this afternoon I can post a low score,' said Rocca, whose last victory came in the 1999 West of Ireland Golf Classic. 'I will try my best and if I can finish in the top five I will be happy.'
Olazabal, who can vault up the Ryder Cup standings with a win this week, turned in a third-round 66 that included three birdies over his last five holes. He holed a chip from 35 feet at No. 17 before finishing with another birdie at 18 to claim his spot at the top.
'I havent played all that well this week especially off the tee. Its not very consistent but I managed to score today and that was important,' said the Spaniard, an 18-time European Tour winner who also captured the U.S. Masters title in 1994 and '99.
Olazabal's countryman Domingo Hospital and Englishmen Neil Cheetham and Paul Eales finished round three in third place at minus-eight.
Full-field scores from the Novotel Perrier Open de France