Unfortunately the blog does not currently have this kind of workflow and really I don't recommend publishing a blog on more that one page because the friendly urls for the blogs have to map to a specific page id to enforce page level security. So if a blog post is made from a private page (ie a page that the public is not in a role to view) then the url for the post will have that page id and when a user goes to visit it, the permissions checked will be for the private page and the user will get access denied. I need to beef up the documentation a bit, the multi page puiblishing really only works well for features that are completely contained within the page like Html, Google Map, Links, Xml and some others. Features that have additional supporting pages like blog, forums, WebStore, can have some issues if published on more than one page unless all pages have the same permission and always will.
I have it on the roadmap to implement workflow and have already done some of the initial design. Some of it will be in the core to handle workflow on page objects, but also workflow will have to implemented as part of the feature to handle workflow for content items. I may add it into the blog or spin off a new feature from the blog since it has most of the needed functionality already.
The only thing I can think of that could get close to this workflow now is if you used a Feed Aggregator to publish the blog by aggregating the feed from the blog. The feed manager could only be edited by the admin and you would enable the setting in Feed Manager for selective publishing. This allows you to pick which posts from the feed are published on a post by post basis, whereas with selective publishing disabled all the items in the feed will be published. I'm not 100% sure if the feed from the blog will work if the blog is on a page that is restricted by roles though.
Hope it helps,