Google Cloud IAM does allow you to handle groups of users - and assign roles to entire groups.

However, these groups are NOT created within the cloud console.

These groups are created in Google Workspace (formerly gSuite).  Only admins that can get into the admin.google workspace can create or edit or delete groups.

Once created, these groups show up in Google's cloud console. Roles can then be assigned just like regular IAM user roles from here on.