DON'T hit the rotor with a metal faced hammer!!!!

Use a "dead blow", or rubber faced hammer, as Rockledge suggeted, or use a wood block in contact with the rotor, so you don't "dimple" it's surface.

You might try some heat, from a heat gun, at the hub & stud areas, to help with parts expansion, that'll help loosen the rust & aid the penetrating oil to do it's thing.

Just some more thoughts for consideration.

Let us know how it goes.