To create a custom role, in your Google Cloud console, navigate to IAM & Admin > Roles. Click + CREATE ROLE.
Name the role, for example: Custom VM Start/Stop Role.
Alternatively, you can provide the Viewer role for the required service type and Monitoring Viewer role to perform resource discovery and monitoring for that service type.
For example, provide the roles Compute Viewer and Monitoring Viewer for the service type Compute Engine to discover and monitor the Compute Engine resources.