Never a problem here using Ceni in a Trinity session. I don't use any other network setup apps, only ceni, wpa_gui or manual configs.
Ceni should be called in a root terminal. It should not matter what desktop. What actually happens when you run it in Trinity?
Regarding wpa_gui, it's really good if you use more than one network. Once setup it just connects automatically to the first available. A user can edit/add networks quickly and easily. It has scan function also. It's qt4 but doesn't need many deps
But it doesn't configure your interface, just networks. You have to edit /etc/network/interfaces and /etc/wpa_supplicant/wpa_supplicant.conf manually one time only.
Offtopic for this thread, but are you saying you can use kdesu (it's not a package in itself) without a problem,?
I cannot without the fix I mentioned before, it crashes kdeinit. With or without sudo-trinity installed.
For example, how do you open kwrite, konqueror, kuser, synaptic or other X apps as root?