Download the R15IK Blender archive and open it, you will see a Roblox Rig and a bunch of others things. Must be something like this Now, let's see how to animate with the Rig.

Roblox GFX are high-quality images with graphics that look far better than anything seen in-game. Using Blender, the free and open-source graphics software used primarily to create animated films and ...

I'm using the blender add-on Auto_rig_pro to rig a KOIKATSU model, but I'm having trouble with an error like this. Does anyone know of another method or solution?