I want to call the API to get the (Cost vs. ROAS) forecast.

It's visible on GA-FE, but the response object doesn't contain the ROAS or any value metric.

GA_FE:

API:

https://developers.google.com/google-ads/api/reference/rpc/v11/ForecastMetrics?hl=en

Any idea how can I calculate the (Cost vs. ROAS) forecast.