It looks like you're not initializing resque. To do so, you need something like the following:
# config/initiazlizers/resque.rb
uri = URI.parse ENV["REDISCLOUD_URL"]
Resque.redis = Redis.new host:uri.host, port:uri.port, password:uri.password
This initializer reads your URL from the Heroku environment variable that was set by the rediscould add-on, parses it, and passes it to Resque so it connects and authenticates with the redis server.