Rozner shot an eight-under 64 on Friday to join Garcia-Heredia and Valimaki in a one-stroke lead — at 10-under 134 overall — after two rounds at Mont Choisy Le Golf on the Indian Ocean island.
"I like the place I think," said Rozner, a 29-year-old Frenchman who was a runner-up to Rasmus Hojgaard after a three-way playoff in 2019, the last time the tournament was held.
"Once you're off the course, you're completely disconnected ... That suits me well. My girlfriend is here. It's a lot of fun for us."
Garcia-Heredia, a 40-year-old Spaniard in search of his first European Tour title, made seven birdies and one bogey in his 66.
"When I can go fishing afterwards or in the mornings, it relaxes me," he said. "It's going well. I'm playing good, putting good."
Rozner had eight birdies and said it was one of the few times in his career that "I'm happy with every single score on every hole."
Valimaki was the overnight leader after a course-record 62, but the Finn's second-round 72 mixed five birdies with three bogeys and a double bogey.
South African Oliver Bekker (71) was one shot off the lead and the trio of Casey Jarvis (67), Christoffer Bring (69) and Pierre Pineau (71) were a further stroke back.
Three of the previous five editions of the tournament were decided by a play-off. The event was cancelled the past two years because of the COVID-19 pandemic.
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