Calories Added to Grilled/Sauteed Veggies?

My two favorite ways to make veggies (broccoli, peppers, onions, squash, carrots, etc) are to stir fry them with a little olive oil, or to marinate them in Newman’s Own Light Balsalmic Vinegrette and then grill them while I grill whatever meat is for dinner that night. I’m trying to figure out how to accurately figure how many of the fats from the oil or dressing are making into the food…

On a similar note, I like to roast sweet potatoes in spices and oil and can’t figure out how many calories the potatoes gain from the oil.

Anyone have any good references or thoughts for solving this?