How do you feel about me roasting my sister for only enjoying plain food?
Why do you want to make fun of her for liking plain food?
Because she's always telling me how repulsive she finds most food and it annoys me.
I imagine that it is frustrating that your sister makes negative comments about her food, but you shouldn't respond by making fun of her eating habits - two wrongs don't make a right. In either case, making fun of what someone eats is hurtful. Instead, share how her behavior makes you feel.
It's not that big of a deal.
You're right, it isn't a big deal which is why you shouldn't roast your sibling. It just doesn't make any sense to hurt someone that you're meant to care for, even if she annoys you sometimes with her eating habits.