Here is my reply:
I doubt you are confused from what the Bible says. I would imagine you are confused at what religions are saying. Let's talk about what determines if a person goes to Heaven to be with God or separated from God in hell. A person is saved from his or her sin when they confess that Jesus is the Lord and believe in their heart that God has raised Jesus from the dead. (Romans 10:9-10) It goes on to say in that same passage, "everyone who calls on the name of the Lord will be saved." (Romans 10:13) The Apostle Paul also said in Ephesians 2:8-9, "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that not one may boast."
From these scriptures we understand that our salvation is not through good works but through the sole sacrifice of Jesus Christ. Those that receive Him are saved and will be with Him. Those that reject Jesus are lost and without Him. There is no sin outside God's reach of forgiveness. There is no sin that cannot be covered by the blood of Christ through his sacrifice. The question is this, Did you receive Jesus and what He did for you on the cross or did you reject him and take matters into your own hands. Romans 3:10, states that we have all sinned and fallen short of the glory of God. Therefore, we are all guilty. If you don't receive forgiveness through Jesus you must pay for your sin on your own.
I have no idea if Robin Williams ever accepted Christ as his Lord and Savior. But I do know that God will not send him to hell because he committed suicide. When we listen to the words of the Lord there is grace and mercy for every situation. When we listen to religion we find ourselves outside of God's grace and mercy.
There are religions that teach you must ask forgiveness for all your sins and if you don't you go to hell. Therefore if one commits suicide they don't have the opportunity to ask for forgiveness and have perished in their sin. This does not agree with the message of grace and salvation taught is God's Word. Truthfully there is no way to ask for forgiveness for all of our sin because we don't even realize half the sins we commit. In this line of thinking we are all damned because we have all forgotten at least one. But salvation by grace through faith covers all our sins and leaves nothing to chance. Jesus paid it all.