rotors

Assuming you have been driving the vehicle it's unlikely the surface that is used for braking is rusted. Any rust gets rubbed off when you brake. My guess is they are trying to screw you. Brake jobs are often an easy source of revenue because they can sell you on FEAR of bad brakes if you don't let them replace/repair every imaginary flaw.

If they are trying to remove the rotors to resurface them, it is entirely possible. A proper brake job includes either resurfacing the rotors or replacing them with new ones. It is completely common for these things to be difficult to remove due to environmental rusting.

If you want a proper brake job either find a mechanic that has an on-the-vehicle resurfacing machine or purchase new rotors. Personally I would rather spend my money on a new set of rotors...

Good luck,

Steven