Hi together,
I google a lot around and replaced my mainboard until I found out that it's definitly compatible and works like a charm.
So common mistakes are:
Connect BOTH! power plugs. ATX and 2x4 CPU!!
When the CPU-LED is red, when you start your system, you have to flash your bios to the newest version.
If you have .ROM Bios installed, you have to flash the .ROM to .CAP Converter first:
Rampage-IV-Extreme-CAP-Converter at
http://www.asus.com/de/Motherboards/RAMPAGE_IV_EXTREME/#support_Download
Put it on an USB-Stick (FAT32) and rename it RE4.ROM. Plug it in and hold the ROG Connect for 5sec. Then the LED should blink SLOWLY for a while. Wait until it stops blinking.
After that you can put the current bios version to your USB-Stick and rename it to RE4.CAP. Plug it in and hold the ROG Connect for 5sec. Then the LED should blink slowly for a while. Wait until it stops blinking.
You're done and your system should boot now!