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.

This project creates a character animation rig using a script that automatically applies Inverse Kinematic constraints on specified bones of a human Metarig from Blender's Rigify Add-On, effectively ...

In Blender, a popular and free software for 3D modeling and animation, you can rig your character with bones and constraints, which are tools that define the structure and behavior of your skeleton.