In a medium bowl, mix the rose syrup, milk, and rose water. Taste and adjust sweetness by adding 1 or 2 tablespoons of sugar if necessary. Set aside.
In another medium bowl, add cold mascarpone cheese, 2 tablespoons powdered sugar, 2 tablespoons heavy cream, rose essence, and red food color. Using a hand mixer, whip for at least 45 seconds until smooth and lump-free.
In a separate large bowl or stand mixer bowl, whip the remaining heavy cream for 30-45 seconds. Gradually add powdered sugar, 1-2 tablespoons at a time, and continue whipping until soft peaks form. Scrape down the sides as needed.
Once soft peaks form, add the whipped mascarpone mixture all at once. Continue whipping until stiff peaks form. Be careful not to overwhip; the cream should be firm but spreadable.
If the cream becomes too warm, refrigerate the bowl briefly before continuing.
In an 8×8 dish, begin layering the tiramisu. Quickly dip each ladyfinger in the rose milk mixture for 1-2 seconds before laying them tightly in a single layer at the base of the dish.
Spread half of the mascarpone cream mixture evenly over the ladyfingers using a spatula.
Create another layer of dipped ladyfingers and top with the remaining mascarpone cream.
Optional: Reserve a small amount of whipped cream to pipe on top for decoration.
Refrigerate the tiramisu for at least 6 hours or overnight. Before serving, decorate with rose buds and slivered pistachios as desired.
To serve, slice with a sharp knife and lift portions using a flat spatula.