How to root Samsung Galaxy Alpha SM-G850A? Seems I have searched vastly across the internet to no avail.

So far, I've tried using a CF-auto-root file with Odin 3, and vroot, neither of which worked. The only helpful thread I've found was an XDA thread from may 2015 which still did not seem to help

http://forum.xda-developers.com/galaxy-alpha/help/want-to-to-root-alpha-sm-g850a-t3107199/

The only other resource I've found were several forums and websites that link back to the same blog that claims to have rooted the phone, but the download file is labeled as malicious by chrome and there is no conformation by anyone that it actually works.
You may need to unlock the bootloader before doing this process. Here is tutorial.

As you mentioned above about odin , it means you know how to work with odin. Now just download this CWM recovery file and flash it using Odin.
Now download this flashable SuperSu zip.. Move this SuperSu zip to your sd card. Now you have to boot in recovery mode after flashing CWM recovery. In recovery mode install this zip file and reboot.

This is the best way to root any android.