Does baking or roasting food in the oven kill the nutrients?

Heat reduced vitamins. But on the other hand, softer vegetables are easier to digest so more are absorbed. Also boiling vegetables can end up with the vitamins in the water that you throw away.

So some foods are best eaten raw, some best steamed, some best roasted.

Fruits and salad vegetables should be eaten raw. Some vegetables can be shredded or spiralized too.

Broccoli, peas should be steamed.

Potatoes should be boiled or roasted.

( Beans can't be eaten raw by the way, they have to be boiled or in a casserole ).

No, all cooking methods destroy some of the nutrients, but it's not a huge amount.

Raw doesn't always mean healthy.

Louise Pasteur figured THAT out 165 years ago.

Foods that have never been heated or radiated may contain a number of deadly pathogens so i will ALWAYS at a minimum thoroughly rinse them and pop them in the microwave for a few seconds just to kill anything that may be on or in them.

Assuming you speak of vegetables, some vegetable cannot be baked/roasted, like peas(unless you want marbles), salad greens, etc, while other are wonderful baked/roasted, like butternut squash, potatoes, even Brussels Sprouts.