root_url should not be provided with this type of parameter. It is logical that it does not work.
Run rake_routes in the console to get the correct names for your routes.
One ugly workaround that fits your needs would be:
<%= link_to page.name, root_url + page.name %>
Last question: why are you using root_url instead of root_path ?
The former tend to uselessly pollute their views.
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