And superstitious '12+1' world champion Nieto - six times ruler of the 50cc class in addition to seven 125cc titles - played a central part in Rossi's post-race celebrations.
The Spanish legend of the '60s, '70s and '80s - dressed in special leathers saying 'Bravo Valentino' - took control of Rossi's victorious Fiat Yamaha on the slow down lap, while The Doctor sat behind him waving a '90 +90' flag.
Rossi's next record-book target will be the four wins he needs to match countryman Giacomo Agostini's all time premier-class record of 68, although Ago's total of 122 wins in all classes will take some beating.
Sunday was also a dream day for the Yamaha factory, which swept all three podium places. Rossi finished almost five seconds clear of injured team-mate Jorge Lorenzo - who rode an incredible race after slipping back to tenth on the opening lap - with Colin Edwards third for the home Tech 3 team.
By contrast, Dani Pedrosa saw his repeated attempts to take the lead thwarted and was eventually shuffled back to a disappointing fourth position, while world champion Casey Stoner dropped out of the podium fight when a mechanical problem five laps from the finish ruined the Australian's perfect record of 22 point scoring rides for Ducati.
Add in some frantic battles throughout the field, plus a mid-race rain shower, and there was more than enough to keep the vocal French crowd entertained for the full 26 lap distance.
Rossi had been only sixth through turn one, as Stoner and pole sitter Pedrosa took the early advantage. Pedrosa's rivals had feared the Repsol Honda rider might escape if he broke clear in the early stages, but Dani was unable to find a way past Stoner - and came close to losing the front of his RCV when he finally attempted to dive inside on lap four.
The 2007 world championship runner-up saved the head-shaking incident, but ran wide and was promptly attacked by Rossi. Pedrosa put up a stiff resistance, but the Italian confirmed the move at the following turn.
Rossi then spent three laps behind Stoner, and saw his first attempt to overtake the #1 firmly rebuffed when Casey ran the seven time world champion to the edge of the track. But on lap eight Rossi made a neat victory pass up the inside of Stoner on the entry to an off camber left hander, and had built a three second lead by the halfway stage.