Hi,
I believe, the function should be mentioned here along with the info on how to get urls for parameterized routes and an example of calling the function from a Twig template (for both parameterized and non-parameterized routes). The python-like syntax for hash arrays might be tricky for the newcommers.
Currently, some info on route_url is present in the Config section of the docs. I believe this section should have a link to the full page covering Routes.