This is a very simple module that offers a block type called "Conditional Content Block" that offers two text fields (with WYSIWYG). The site editor is able to choose a single role that will have access to each field. The most common use case would be one message for unauthenticated users and another for authenticated users. But, other combinations are possible.
Please, offer feedback and ideas in the issue queue.
Pull Requests are welcome.
This project is GPL v2 software. See the LICENSE.txt file in this directory for complete text.