You can now configure a new event in Meta Ads Manager to track purchase conversion from new vs return customers. You may also edit this new metric to track new and return customer ROAS, and populate this information directly in your campaign reports.

1. Verify your 2 new custom events: NCPurchase and RCPurchase

NCPurchase tracks new customer purchases. RCPurchase tracks return customer purchases.

2. Create the custom conversion, and share it with your ads account

3. Create NCPurchase ROAS Metric in your campaign report