we already have psSphereRotConjugate to apply the inversion to a given psSphereRot object. The original definition of this function is somewhat redundant with that function. I'm accepting the psLib code version and have changed the SDRS to match. We thus have two functions:
psSphereRot *psSphereRotConjugate(psSphereRot *out, psSphereRot *in)
and
psSphereRot *psSphereRotInvert (...)
where the first inverts the psSphereRot in hand and the second constructs an inverted one based on euler angles.