Custom Rom Without Root topic

So I looked around and couldn't find an answer on this, but I am in a situation where I can't have a rooted phone if I want to access my corporate email which is very important.

On the the problem. I really want to flash a custom rom, but they all obviously are rooted. Is there anyway to unroot a custom rom? I really don't need root access, but I do want to flash a kernel and Pure Shamu if possible.

Any help would be awesome. Thanks in advance!