Disclaimer: We do not have any means of testing rift controls, or any reference as to what the controls are so this attempted additions may not make the game playable on rift, but due to player feedback we are attempting to add support.
I have no way to test this at all, and can't find any kind of comparison for controls for the Rift as opposed to the Vive, but here is how I am assigning buttons in the update that is about to be uploaded to attempt to add support for the rift. (right hand only at this time, don't want to mess with movement modes that seem to be working).
Right trigger - same as vive trigger
Spell Trap - thumb stick cap touch
Spell projectile - b button cap touch
spell draw - a button cap touch
spell AOE - thumb up cap touch
As stated, i don't know if this is going to cause issues or not, I am willing to work with anyone that is willing to test it out for us to try to get it working, otherwise there won't be official support for the rift until i actually have one on hand to test with.