The only time you need root access in Linux is if you're making changes beyond /home. Settings in Gnome/KDE/Xfce, etc. are stored in the user's home folder so no root access is necessary. It's only when you make system-side changes like GDM settings or network settings that you need to sudo or just input a password through a pop-up prompt. apt-get (or the equivalents in other distros) also require root access.