A minimum of for my reasons, it's essential that the Contributor be not able to edit his posts once they have been scheduled to become released, in addition to really released.

This appears like it ought to be simple because otherwise inside a system with many different customers a malicious user could slip individually distinct having a sketchy publish beginning with posting an innocuous one after which right prior to it being scheduled to become released, edit it.

No role-editing plug ins I have attempted appear to possess this functionality.

You have to produce a filter function add hook it.

You might want to read "WordPress tip: Allow contributing factors to upload files" at http://www.wprecipes.com/wordpress-tip-allow-contributors-to-upload-files to obtain a concept.

The filter hook you will need may be the "format_to_edit" hook. Please make reference to http://codex.wordpress.org/Plugin_API/Filter_Reference for particulars.

That filter hook is not what you would like. Allow me to consider it.