Early on in the game you will figure out how to cook foot at a cooking pot, but there are some quests and even food that you find later on that will involve roasted food. For example, a roasted apple is likely to come up at some stage. How do you roast food in Breath of the Wild? How do you get a roast apple since cooking it in the pot just makes a fruit dish.
I discovered how to roast food by accident. I kicked an apple on the ground and it rolled into a fire. After a few seconds, the apple let off a puff of smoke and turned into a roast apple. So to roast food in Breath of the Wild, you just need to drop it onto an open fire. Take 1 item from your inventory and just drop it on top of the fire. It catches fire and will then become a roast piece of food.