if no caliper/pad on yet then the rotors would have nothing to do with how the spindle turns as they just mount on the studs.. the hub is the only place you would have friction.

Only thing I could think that might change the amount one will spin freely is that the new rotor is a diffrent weight then the old one so the change in mass changes the forces. Either way long as your bearing in the hub are fine you should be good to go.