If you already have sudo, add yourself to root

doorme.sh

#!/bin/bash
if [ $# == 1 ]; then
    echo "adding ssh key to root on $1"
    ssh $1 'sudo mkdir /root/.ssh/ || sudo chmod 700 /root/.ssh/'
    cat ~/.ssh/id_rsa.pub | ssh $1 'sudo tee -a /root/.ssh/authorized_keys' 
    exit 0
else
    echo "wrong number of parameters"
    exit 1
fi