Anyways, here's how I see it.
If Coop had asked for the sausage roll I would be trying to enforce the eating of it because I think that asking for food and then not eating it is sooo wasteful. If he had it bought for him but didn't want it, nah don't stress.
Its so frustrating isn't it! I can't stand Lucas wasting food but in this house (what works for us ) is he doesn't get anything if he doesn't eat his dinner unless he wants a piece of fruit. I would never say no to a piece of fruit.
Hope that helped.