Certain types of cookware and pans are prone to rusting, especially enamelware and cast iron. Enamelware is essentially a layer of colored porcelain applied to the top of a cast iron pot. When you leave the pot sitting outside, in a sink full of water or simply soaking on the stove, you risk rust forming. Rust on a roaster pan poses few dangers to your health but is harmful to the pan.
A small amount of rust may occur from water left sitting inside the pan or touching the sides of the pan. The longer you leave the water sitting in the pan, the worse the damage gets. Rust is a type of oxidization, and the rust will slowly eat through the pan. If you remove the water and clean the roaster pan as soon as possible, then it is possible to stop the oxidization process. If you leave the rust untreated, however, it will slowly spread through the pan. The rust can actually form large holes in the pan and spread, ruining the pan.
An old wives' tale or urban legend claims that consuming rust may lead to tetanus. If you consume a large amount of rust, tetanus is a possibility, but it should not happen from the small amount of rust that rubs off the pan and onto your food. The only way you could develop tetanus from rust is if the rust flakes off the roaster pan in large chunks and gets into your food.
According to Care2.com, a small amount of rust poses no potential health problems. Even rust in your water caused by old rusty pipes does not cause any health problems. The main component of the rust is iron, which the human body needs for growth and health. However, rather than eating off of rusty utensils or cookware, take an over-the-counter nutritional supplement that contains zinc. Consult your physician and determine if you have an iron deficiency before taking any supplements.
While rust is not necessarily dangerous, it does change the taste of food cooked inside the roaster pan. These trace amounts of rust may give your food a slightly coppery taste that you may not like. Clean the rust from your pan with steel wool. Pour a small amount of water into the bottom of the roasting pan. Run the steel wool through the water, lightly coating it with the liquid then scrub the rusty spots. Rinse the pan with fresh water and dry it thoroughly before using.