Mix the mayonnaise, seasonings and water. Add the potatoes, (I put it all in a plastic bag.) Toss to coat the potatoes. Place the potatoes on a greased cookie sheet.
Bake at 400 degrees for 30 - 40 minutes, or until golden brown and tender, stirring after 15 minutes. Note: Oregano can be substituted for all or part of the rosemary if desired. I have also made these with dry ranch dressing mix and Lipton onion soup mix (dry.)