Where is the rust at? If it is on the outer edges and/or on the hat area (part in the center where the brake pad does not ride), there's probably absolutely nothing wrong with the brake rotor in the first place. As long as the wear area where the pad does it's business is clear, you have no issues. Only brake rotors which have been treated with some type of anti-rust agent (like zinc plating) will not rust in these areas.
If on the other hand it is where the pad should be riding at, you may (as @Paul was suggesting) have an issue with your caliper being stuck or possibly not sliding correctly on its pins. Since you said you don't have any means of removing the brake rotor yourself, you'd need to take it to a brake/mechanic's shop to have it fixed.