Roasted watermelon seeds come packed with iron. Just an ounce of seeds contains approximately 2 milligrams of iron -- 25 percent of the recommended daily iron intake for men and 11 percent of the RDA for women, according to the NYU Langone Medical Center. Iron helps you make hemoglobin and myoglobin, proteins that help transport and store oxygen in your tissues. Iron also promotes liver function and nourishes your immune system.