This is quite weird... I created few roles starting from a copy of the default Author role and such roles have the same capabilities of authors plus a couple of more things. When I create a post as admin and want to assign it to one of the users who belong to those roles they do not appear in the list. So I have to set the user back to Author, edit and update the post, then set it back to the proper custom role.
Does anyone know why is this happening? Is it the way it is supposed to be?..'cause it seems like wp do not understand that these custom roles have all the necessary capabilities to publish posts.