the rootless package is not build with the same flags, the suid_wrapper is turned to false. Then the sticky bit of X binary is modified, see
https://wiki.gentoo.org/wiki/Non_root_Xorg on the Alternative section.
So, now i can launch X with my user
obarun 915 0.0 0.0 16040 1012 tty1 S+ mai25 0:00 xinit /home/obarun/.xinitrc -- /etc/X11/xinit/xserverrc :0 vt1 -keeptty -auth /tmp/serverauth.bdy2m7Ykl2
obarun 916 1.3 1.9 495924 158756 tty1 Sl mai25 20:17 /usr/bin/X -nolisten tcp :0 vt1 -keeptty -auth /tmp/serverauth.bdy2m7Ykl2
as you can see X and xinitrc is owner by the user obarun.
To start my X server (not automatic login here), i log on with my normal user and i type startx and that's all.No sudo no su or whatever.