Community Support Forums

I just want to do one simple thing; I don't want to protect content, but I want to charge for allowing users WP roles, eg :
Free to be a Contributor – Somebody who can write and manage their posts but not publish posts
Paid to be an Author – Somebody who can publish and manage their own posts

- without Admin manually editing roles.
Is this possible with S2Member?

s2Member is not right for this. s2Member locks down access to editing roles.

Thanks Any suggestions?

Thanks for the great question.
I suggest using one of s2Member's Roles, and modifying it so that it includes access to the Capabilities needed by a wouldbe Contributor, and/or Author. You can do this with a plugin such as the Capability Manager: http://wordpress.org/extend/plugins/capsman/

I'm using this capability manager from Justin Tadlock to customize capabilities/subscription levels. http://wordpress.org/extend/plugins/members/

Works great with s2.