When misspelling the root password, the scripts ignores the error and no root
password gets set.

Something like the following should do the trick, feel free to issue some pretty
warning message inside the loop. :)

--- /etc/debootstrap/chroot-script.orig 2007-12-14 10:06:04.835720597 +0100
+++ /etc/debootstrap/chroot-script      2007-12-14 10:06:37.007592595 +0100
@@ -252,7 +252,7 @@ passwords() {
   else
      echo "Setting password for user root:"
      set +e # do not exit if passwd returns error due to missmatching passwords
-     passwd
+     until passwd; do :; done
      echo ""
      set -e # restore default behaviour again
   fi