When you go on your roof, make sure you use the right ladder.
The best one is an extension ladder. You should not use a step type ladder unless you are leaning it against the house and it clears the roof line. You should have at least 3 feet of ladder past the roof line to make sure you have a good grip when stepping on and off the roof. And make sure the ladder is firmly on both feet and stable. It only takes one accedent to ruin your life, so dont let it be easy to happen.