Deriving the answer to this question can get involved. I am giving the formula only and am assuming you are looking for the magnetic field B at the center point of the sphere. If the sphere rotates with angular velocity along, say, z axis, then the formula for B is as follows:
![\vec B_0=(2)/(3)\mu r q \vec \omega](https://img.qammunity.org/2020/formulas/physics/college/i5f5sc752j1kk1lnervqfqal3anm93mwuw.png)
(with mu the magnetic permeability)