Other assets
All of the physical dice roller are based on the bottom face collision on the ground. So you need a ground collider to calculate the result. Also it's impossibile to che ambiguity situations od the dice.
Physical Dice Roller
Physical Dice roller no need the ground collider for the result but use a new approch to calculate the result based on the top face. In this case you can roll the dice on a not planar terrain, obstacles or on different high.
The system uses also an ambiguity check to calculare the right face for the result (when the dice stay "in the middle") and a roll life value to consider null the result.