1. The food is sweet.

2. The food is delicate.
3. The food has a roasted flavor.
4. The food has a delicate flavor(taste)
5. The food has a sweet taste(flavor).
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Are they all grammatical and do they have the same meaning? What is the difference among them?

The sentences are all correct, but they do not necessarily have the same meaning.

The words sweet and delicate might mean something similar, but not sweet and roasted.