rake task for dumping roles defined in the ruby DSL to json. expects dir .chef/chef_server_backup to exist in your chef-repo

chef.rake

namespace :roles do                                                   
  desc 'dump roles defined in the Ruby DSL to json'                   
  task :dump do                                                       
    destination_dir = File.join(TOPDIR, '.chef', 'chef_server_backup')
    files_paths     = Dir["#{TOPDIR}/roles/*.rb"]                     
                                                                      
    files_paths.each do |filename|                                    
      role_name = File.basename(filename, '.rb')                      
                                                                      
      role = Chef::Role.new                                           
      role.name(role_name)                                            
      role.from_file(filename)                                        
      role                                                            
                                                                      
      json_file_path = File.join(destination_dir, "#{role_name}.json")
      File.open(json_file_path, 'w+') do |file|                       
        file << role.to_json                                          
        puts "dumped #{role.name} to #{json_file_path}"               
      end                                                             
    end                                                               
  end
end