It is best to delete to delete the "Read More" links before importing your Joomla! articles into RSBlog!, and add them again in RSBlog!. The Read More links may not be imported successfully and so will not be displayed properly.
However, if the "Read More" links show up correctly in RSBlog!, when viewing the Post in the backend, but are not displayed in the Blog View. Then please make sure that the "Only Display Intro Texts" option(set when editing the "Blog View" menu item) is set to Yes. If the option is set to No, then the Read More links will not appear in the frontend.
In RSBlog! there is no need to add the Intro Text both before the Read More link and after it, just like in Joomla! articles. The Intro Text should be added only before the Read More link in the post.