First, I'm not familiar with that board but does it have a debug button on it or any flash codes. Sometimes you can get lucky and press a button and it will flash a display code and when you check it will give you a list of issues that the board is seeing on its end that be may directly preventing start up. Id also quickly double check ASUS ROG QVL and see that all your components on your board are supported and have been tested by the manufacture.
Secondly, a few people have mentioned that you should check your wiring. This is absolutely a must step when diagnosing a power issue. One thing I've run into is people either not fully connecting a power cable into a socket, or not plugging enough in. Many motherboard instructions are vague at best. When looking at a board ensure that both the motherboard power socket and the cpu power sockets are inserted fully. Also ensure that they are plugged correctly into the PSU. While the motherboard socket is pretty straightforward on the PSU sometimes I've seen people jam the the CPU plug into the SATA or vice versa and use the incorrect wiring to make it fit. People get into a rush and forget to properly plug things in. We are human and make mistakes.
Also while looking at your wiring, double check your case's power button. Cases range from $100 to $500+ and the cheapest component on the entire case is the $1.75 power button. Does the button feel mushy or get stuck?
Next I would go ahead and download the very first BIOS software for your board. Not the latest, but the very first and get it ready to go. Having the latest and greatest BIOS software is great, however sometimes it can produce instabilities with the RAM you have configured or the chip or really any number of issues. There could be bugs within the system. However if you can reflash to the earliest version of your BIOS and see if this eliminates the issue.
If that hasn't done anything I would pull the computer apart and look at the board for physical damage. Specifically what you want to look for its bloated or swollen electronics on the board. Are there any funky smells coming from the case when you try and power it up. Does the board have any discolorations that you could see or any weird blotches on it that don't look like they are suppose to be there.
At that point I would begin the process of pulling the chip and be very careful to look it over. Does the chip look discolored or swollen. When you remove the chip are the pins bent, missing or damaged. Overall what is general state of the chip when you look at it versus when it was installed.
I've never needed to remove the CMOS battery and/or clear CMOS so I can't really speak to that. However 95% of the time it is a wiring issue. Either not fully plugged in, or wire got pinched in a section of the case and got severed or the case power button took a crap. After that it is either a CPU that got crushed into the socket or a board that has failed directly.
Hope that helps!
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