Are There Different Responsibilities and Rewards in Heaven?

Christians understand our salvation is a free gift of God and cannot be earned in any way. But what happens to us in eternity? Do we all experience exactly the same thing? Do all saved Christians experience the same kind of responsibility, joy and purpose? Are there different levels of responsibility and reward in heave, and if so, how are these levels "earned"? Does this notion contradict or undermine the idea that Salvation is a free gift?