Woosnam, the course record- holder, aims to be the first player in Europe to complete a hat-trick of victories in an event since the Australian Peter Thomson won the Open in 1954-56.
On his first shot, played in heavy rain and with low cloud drifting across the 3,000-foot high course, he hit a tree. Although he still bogeyed the hole, he knew it could have been a lot worse and responded with six birdies, the best of them when his seven-iron tee shot to the 165-yard 12th - his third - finished only a foot from the cup.
However, his concentration did lapse on occasions, such as at the seventh when he three-putted from only 20 feet.
Rocca leads by one from Ireland's Paul McGinley. The Italian's best finish on tour came when he was runner-up to Woosnam in Monte Carlo two years ago. Yesterday was not just a return to a happy hunting ground, but also a continuation of where he left off last week when he moved into third place in the French Open on Sunday by playing the last nine holes in 30.
Yesterday he had four birdies in a row from the 14th and picked up further shots on the first and seventh before slipping up at the end with a three-putt.
Seve Ballesteros had tree trouble in his 70. Two under par playing the long 17th, his ball stuck four feet off the ground in some branches. He elected to take a penalty drop, but hit the ball with his shank - a double-bogey seven resulted.
Alongside Woosnam in third place are Keith Waters and Wraith Grant, of England, Ireland's Darren Clarke and Manuel Pinero, of Spain, whose last win was the 1985 Italian Open. Vijay Singh of Fiji had the day's worst single score, an 11 on the par-four third.
Scores, Sport in Short, page 39Reuse content