Rocket League features Cross-Platform progression! You can share your Competitive Rank, Rocket Pass Progress, and your hard-earned inventory across all platforms!
Rocket League’s cross-platform progression is made possible with an Epic Games Account. Creating one or signing into your existing Epic Games Account is the first step of the process. You'll be prompted to do this when you start up Rocket League for the first time. You can also link your accounts using the Rocket League account linking site.
Once you're logged in, you will be asked to set a Primary Platform. Your Primary Platform will be your source of progression (Rocket Pass Progress, Competitive Rank, XP Level) for all of your connected platforms.
For more info on Account Linking check out: How do I link my platform accounts to my Epic Games Account?
Each platform you link to your Epic Games Account shares its inventory with your other connected platforms, with a few key exceptions. As an example, purchased Credits/Esports Tokens are only available on the platform they are purchased on. Credits earned from Rocket Pass will be shared across platforms.
For more info on Shared Inventories check out: What items can be shared across linked accounts?