Contributor cannot Insert Images

I have a blog which has contributors, and their input needs to be reviewed before publishing – I’ve set them up as Contributors. So far, so good.

They need to be able to upload images and insert those images into the posts.

I’ve added the following code to my functions.php file, as discussed in numerous places around the web:

if ( current_user_can('contributor') && !current_user_can('upload_files') )
    add_action('admin_init', 'allow_contributor_uploads');
function allow_contributor_uploads() {
    $contributor = get_role('contributor');
    $contributor->add_cap('upload_files');
}

It seems that the Contributors can now upload images, but they can’t insert those images into posts. So it’s only a 50% useful fix.

Does anyone know what I need to do in order to make it so a Contributor can upload an image, insert that image into a post, and set it as the Featured Image (where relevant)?

When I view the Media Library with my Admin user, I can see the images they’ve uploaded, and the Uploaded To column indicates a link with the post. But from the Contributor’s console there seems to be no way of inserting the image. And, when you click on the Add Media button in the editor you don’t see any of the other images you’ve uploaded to that post.

It makes me think there’s another capability that needs to be added, but I can’t figure out which. Some forum posts and web articles talk of using the Members plugin, or the Role Scoper plugin – however near as I can tell they just offer frontend ways of managing capabilities.

Thanks for any pointers!

Jason