During our time in Rotorua, we experienced several different weather patterns. At first, it was bright and sunny, and I felt at home in a long sleeve shirt and jeans, although quickly this turned into rain. I would recommend layering during this time.
Toiletries and Medical Supplies: Readily available in town.
Wear comfortable shoes as walking is a must do around here.
Hat / sunglasses for a hot sunny day. Sunscreen is a must too.
An umbrella for a rainy day.
Toiletries and Medical Supplies: Can be found in the nearby supermarkets
Photo Equipment: Can be easily found in the town center
Camping/Beach/Outdoor Gear: Can be found but you might want to carry what you have already with you.
Luggage and bags:
You don't really need to carry every stitch of clothing you ever owned for an average-sized trip here.
Clothing/Shoes/Weather Gear: If you go in the winter like I did, pack warm threads.
Toiletries and Medical Supplies: I don't see anything different you would need to stow in your toiletry bag here than to any other country or, for that matter, a short business trip within the States.
Photo Equipment: A 35mm camera with as much film as you think you need will probably suit most folks' purposes.