A light rain shower saw the mechanics spring into life in pit lane, but it wasn't heavy enough to require a change of bikes - and the uncertain conditions only seemed to help Rossi build his untouchable lead further en route
to becoming the first double winner of 2008.
After a cautious start, Lorenzo joined the fight for second - alongside Pedrosa, Stoner and Edwards - late in the race.
The MotoGP rookie overcame his double ankle fractures - and two practice falls - to snatch fourth from Edwards on lap 20, take third when Stoner struck problems along the main straight a lap later, and inflict a satisfying pass on arch-rival Pedrosa for second later in the same lap.
Lorenzo later mounted the podium on crutches, before sitting on a chair, having been the top Michelin rider in the French manufacturer's home event.
Edwards demoted Dani to fourth into the first chicane on lap 22, by which time Stoner's lifeless Ducati was being pushed down pit lane. Earlier rain meant the Qatar winner could change to his second Desmosedici - fitted with race tyres - and at least reach the chequered flag, but 16th place meant no points.
Rizla Suzuki's 2007 event winner Chris Vermeulen
rode a strong race to sit just 1.5secs from fourth position by the halfway stage, but dropped away during the second half of the race to finish 11secs from Pedrosa.
Andrea Dovizioso was almost within striking distance of the Australian at the flag, having collided with fellow rookie James Toseland
early in the race - an incident that sent the double World Superbike tumbling into the gravel for his first GP non-finish.
John Hopkins held seventh at the midway stage, but was forced into retirement when his Kawasaki shed its chain. Loris Capirossi
went on to secure the position, with Nicky Hayden, home hero Randy de Puniet
and Shinya Nakano
completing the top ten.
Marco Melandri suffered mechanical problems right from the start, but took advantage of the rain to change bikes and collect the final world championship point.
Meanwhile, just three points now separated the world championship top three, with Rossi leading the standings for the first time in 2008 heading into his home Italian Grand Prix, while Lorenzo and Pedrosa are tied for second.
Stoner's non score has dropped the Australian a worrying 41 points from the lead.
French Grand Prix:
9. de Puniet
12. de Angelis