Rotation: Calculating Rotational Energy of Sphere with Steiner

[Kruger]

Homework Statement

Consider a spere with momenta of inertia of 2/5*m*r^2 that rolls down a plane surface (no friction). I want to calculate the rotational energy of the sphere when it has speed v0.

Homework Equations

Erot=1/2*I*w^2

The Attempt at a Solution

My only problem is: Do I need to transform my I=2/5*m*r^2 with the rule of steiner, or don't I have to use the rule of Steiner? I would say no.

 

[Kruger]

I'm so confused because sometimes Steiner's theorem isn't used and sometimes it is used for rolling objects. Can you please generalize, when I have to use Steiner's theorem for rolling objects? Would be really helpful.