Puree raspberries; heat berries and brown sugar until mixture begins to thicken. Set aside.
Combine oats, milk, water, cinnamon, and salt in saucepan; boil, then reduce to medium heat. Simmer until liquid reduces and oats thicken. Stir in raspberry mixture and serve in four equal bowls.
Arrange berries, pecans, and petals on top of oatmeal.