First of all, seizures are a neurological disorder, it has nothing to do with the food.
Sure there are triggers. The amount of rosemary used in processed dog food is minute and unlikely to be the culprit (imo) I suggest consulting a veterinary neurologist.
The general rule of thumb is that if the dog is having 1 or more seizures a month the dog needs to go on daily medication.
If the symptoms are related to environmental allergies and your regular vet agrees, ask for a referral to a veterinary dermatologist, for intradermal skin testing.
You can use the search engine here to search both, “environmental allergies” and “seizures”.
