The absence of import/export feature doesn't mean that you need to manually do all the stuff.
1. You click on create role, fill the first few text boxes meant to fill the short & fullnames.
2. Go to the existing site with roles & capabilities defined, edit role. open your browser's console, go to the DOM element with Id, "defineroletable" copy the html as html.
3. Go to the new site, locate the same dom element, replace the same DOM element with the one you copied from your old site.
You can live with Moodle 2.5 with this hack until you upgrade to 2.6