I accidentally found a solution for this. I managed to delete /root by mistake, and just recreated the folder again and changed owner for /root back to root again.

sudo rm -r /root/
sudo mkdir /root
sudo chown root /root

After that, all root-apps here are skinned here

Use 'kdesudo systemsettings' to change colours for root to match your system.

sudo ln -s /usr/lib/kde4/plugins/styles/ /usr/share/qt4/plugins/

should fix