Rinus VeeKay, who took his first IndyCar pole position and scored his first podium at the same venue last October, sat at the top of the times for most of the session.
The #21 Ed Carpenter Racing-Chevrolet turned a 1m10.0624s on its fifth lap of the 14-turn, 2.439-mile track with Josef Newgarden’s Team Penske-Chevrolet sitting just 0.0019sec adrift – the pair of them 0.34sec clear of the field.
Rossi got within the same tenth, having earlier had a trip off road, before his #27 Andretti Autosport-Honda ducked under the 1m10s barrier with a 1m09.8784s on his 11th lap.
Harvey, front-row starter at the venue last year, went second quickest in his Meyer Shank Racing-Honda, also getting down to a sub-69s lap, while Colton Herta left it until his last lap to grab sixth, behind Romain Grosjean (Dale Coyne Racing) in fifth.
Rookie Scott McLaughlin made it two Team Penske-Chevrolets in seventh ahead of Ryan Hunter-Reay in the third Andretti car.
Graham Rahal survived a puncture and a spin to claim ninth but was unhappy with his car’s handling, while Conor Daly in the second ECR-Chevy claimed 10th.
Will Power, five-time IMS road course polesitter and four-time winner, was only 13th fastest but still ahead of championship leader and defending champion Scott Dixon.
Also looking uncharacteristically slow were the Arrow McLaren SP-Chevrolets of Pato O’Ward and Felix Rosenqvist. Their temporary team-mate, Juan Pablo Montoya – who hasn’t started an IndyCar road course race since 2016 – was 0.6sec off Rosenqvist, but a couple of tenths ahead of ex-NASCAR driver Jimmie Johnson in the Ganassi-Honda. He took the checkered flag twice, so will be forced to sit out the first five minutes of second practice.
Following Max Chilton’s Carlin-Chevrolet withdrawal from the weekend, the car count in opening practice was further reduced when Alex Palou’s Chip Ganassi Racing-Honda sprung a water leak and was towed back to the garage area.
Sebastien Bourdais’ AJ Foyt Racing-Chevrolet ground to a halt on its third lap due to an electrical problem, and therefore was penalised for five minutes having caused a red flag. That was a moot point, however, as he never returned to action.