Here's a way you can simulate transitioning to and from the roof without leaving the ground.

Set a kitchen chair in the middle of the room. Place some masking tape on the floor: one piece about 6" behind the chair yet parallel to the back (and as long as the space between the legs); and two more pieces from the back legs straight out each side.

The masking behind the chair represents a ladder rung. The tape going out each side represents the edge of the roof.

Standing behind the chair on the "rung", hold onto the back of the chair and carefully step around the chair onto the "roof" (and back) without stepping on or behind the tape representing the roof line. Use the chair for stability, but practice doing this until you can confidently do the motion without moving the chair.

Once you've mastered this, place the chair so the back legs are on the edge of a raised platform (say, 4-6" high). A porch or deck might suffice, or maybe the curb at the edge of the street. Place masking tape or a chalk line behind the chair, just like before. The difference this time is that you'll be stepping off of the "rung" onto the "roof" (the raised platform) at a different height. Practice this a while.

Remember, when you are on the "rung" your toes need to point toward the "roof.

This way, you can practice the movement in a safe environment without fear of falling a long distance. It might help you build skill and confidence.

Here's a bonus: you might find that the ladder is actually a bit easier since the ladder will be leaning away from you (giving you more space) whereas the chair back typically leans toward you (encroaching your space).

Just remember: you have to do this without moving the chair (in practice) or the ladder (in real life).