The rotor dont freeze first of all. The caliper can seize up. This could be from a seized caliper but its more likely you have neglected your brake pad service. If you let the pad get to thin it will eventually wear down to the metal backing plate on the pad and grind the plate against the rotor. If its not pulling towards which ever side this is on its not sized its just metal to metal when you apply the brake. New pads and rotors (on both sides) will totally fix this. But if you continue to drive it that metal backing plate will eventually slip out and youll destroy your caliper and loose most of your braking power. Just so you know for next time when you hear your brakes start to squeal every time you brake. Its time for pads. That squeal comes from a part of the pad called the squealer bar and is designed to make the noise when the pads are near the end and is time for replacement.