You can cook and use the microwave on the sabbath.
The sabbath keepers like the SDAs and the rest of them arent ACTUALLY keeping the sabbath though. They are pretending to do so, but biblically speaking, they are not doing it. There are many regulations for keeping the sabbath, not just "resting" on a particular day. And the rest pertains not only to you, but to people in your city, your animals, etc.
Remember this phrase: Its the NEW COVENANT or NO COVENANT