I would not expect my child to eat a sausage roll, or chips or a piece of cake. I place expectations on them to finish healthy foods and they know this.
If someone buys them something that is not healthy then I actually don't care if they don't eat it. They can ask me for something else as i will give them something like fruit or a healthy sandwich.
I don't want them developing bad eating habits so it wouldn't surprise me if they refused to eat something like that.