Maybe you don’t need to set something relative to ground. I can’t make out the 4 bodies shown in the Outline by color in the viewer. I only see 3 differently colored bodies. If the sphere is its own body, with spherical joint to vertical shaft and revolute joint to horizontal shaft, I could see how you would have this problem. If the sphere is connected to the vertical shaft as one body (or fixed joint), with a spherical joint to the horizontal shaft, then imposing a rotation in the spherical joint around the horizontal shaft would work the way you want.
Actually, you could simply this further by having the vertical shaft fixed to the top mount (that also looks like a wheel shape), so there would be only one joint in the model, the spherical joint. Apply the joint load to the spherical joint. You could even get rid all all bodes, except the lower wheel, and use a body-to-ground spherical joint.
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