You can change the appearance of your face but only to the extent that muscle and fat will allow. If you want to decrease the roundness it might be possible to do so with weight loss through exercise. Unfortunately, you can't target fat loss in a particular area because your body loses fat just the opposite as it gains it. If the first place you show weight gain is in your face that will be the last place you'll lose it. But I've seen a lot of people who exercise frequently who have very lean faces.
The only way I know to dramatically change your face to be exactly the way you want is through surgery. That's why so many of transwomen opt for FFS.
Julie