By default the bundle comes with the edit-area (http://www.cdolivet.com/editarea/) JS plugin, which is by no means a WYSIWYG editor. Hovewer, you can load any tool you like by overriding the TheodoRogerCmsBundle::editor.html.twig template.
Just create a editor.html.twig file in app/Resources/TheodoRogerCmsBundle/ and insert there the JavaScript code needed to instantiate your prefered WYSIWYG editor.