Custom Roles & Permissions on Non-Enterprise Spaces

Hello everyone,
we are currently evaluating whether we can use Contentful as our main CMS for a medium to large client. We have some questions regarding the roles and permissions included in the On-Demand/Basic pricing plans:

  1. Are custom roles and thus custom approval workflows only available on the Enterprise plan? We’d actually like to have something similar to the workflow described here:
    Admittedly, we have a very limited budget to start out on, so it’s not an option to purchase the Enterprise plan.
  2. If we go with a Basic plan—e.g. the “Small space”—we get two roles, namely “Admin” and “Editor”. Is it possible to customize these roles a bit? We need to differentiate between people who can only create new content, edit it and others who can create, edit and publish. Our editors should not be able to publish content, is that possible with a “Small space”?
  3. If the Basic plans do not include a possibility to edit roles & permissions as described, which is the cheapest option we have that includes it?

Thanks for you help!