How to make this electrical main safe
No. There is nothing you can, or should do to fix this.
Don't touch it, don't go near it, don't even look at it anymore.  Get off the roof, and call the local power company or an Electrician.
Service entrance cables do not have overcurrent protection and will shock you until the transformer blows, the wire burns and breaks, or contact with the line has been broken. All of which will likely happen long after you are dead.