This page is our investigation of cross-play game Rocket League. We always verify information manually using official sources - no AI.
Yes, Rocket League supports cross-play between all available platforms. Players on PlayStation 4, PlayStation 5, Xbox One, Xbox Series X|S, Nintendo Switch, and PC (via Epic Games Store) can play together.
Information about cross-play in Rocket League is from the official game blog; you can check it for yourself by following the link.

Worth mentioning that initially, Rocket League didn't have cross-play support, and it was added later, on January 14, 2019.