module Roda::RodaPlugins::Static

def self.configure(app, paths, opts={})

and set the :root option to be relative to the application's :root option.
Load the Rack::Static middleware. Use the paths given as the :urls option, 
def self.configure(app, paths, opts={})
  opts = opts.dup
  opts[:urls] = paths
  opts[:root] =  app.expand_path(opts[:root]||"public")
  app.use ::Rack::Static, opts
end