The Custom Repository Roles REST API has moved to general availability, with a breaking change to the path used.
Previously, the API was found at /orgs/{org}/custom_roles – it has been moved to /orgs/{org}/custom-repository-roles. With organization-level custom roles in progress, we found that the custom_roles path was wasn't specific enough and could generate confusion.
The deprecated beta API will be removed from api.github.com in 6 months, on September 7th, 2023.
On GitHub Enterprise Server, the API will be available at its new path in version 3.9. The previous API to list roles was added in GHES 3.4, and will be removed with the next API version.

To learn more about custom repository roles, see "About custom repository roles" and "Custom repository roles REST API".