You could check the "express-on-railway" extension for express.
It comes with a command line tool that has a "print routes map" feature which you could use for that.
That said e-o-r constraints you to a precise directory/file layout I think, which might not be ideal if your website is already up.
Having to do this, I would strongly consider writing the code myself. You can access pretty much all of your routes information through app.routes.routes. Ordering them alphabetically and grouping them by verb should be pretty straightforward... (There might be a faster/cleaner way to do it though.)
-Olivier