Unfortunately the ROK is not designed to go through the dishwasher because the salts will destroy the high quality finish. You can use white vinegar to remove rust. This link may help: http://www.wikihow.com/Remove-Rust-from-Metal. Thereafter, fairly regular (depending upon usage) cleaning with soapy water and thorough drying should keep your ROK in excellent condition. Full cleaning instructions can be found under the FAQ section of our website.
If the vinegar does not work, I would suggest trying a metal cleaner to remove the oxidisation followed by a metal polish. A good hardware store should be able to help you find a suitable non-scratching cleaner.
Note that the water/coffee does not come into contact with this part of the machine during use. The passage of water through the machine touches only food grade polymers and steel and any marking is purely cosmetic