The announcement comes a month after the Swede won the racing classic Indy 500 with Meyer Shank.
Rosenqvist has driven for the team for the past three seasons. Previously, the 34-year-old has raced for Chip Ganassi Racing and Arrow McLaren.
It is unclear which team will be next.
Rosenqvist is sixth in the overall IndyCar standings. The season ends with a race in California on September 6.
