Add milk and rose petals to a saucepan set over low heat. Let mixture come just to a simmer and then remove from heat and cover. Let sit for about 30 minutes to infuse rose flavor into milk.
Pour milk through a fine mesh sieve into a bowl, leaving rose petals behind. Stir in vanilla and pin food coloring, if using.
Pour mixture back into saucepan over low heat. Add in white chocolate and stir until chocolate is completely melted and mixture is smooth. Be sure not to let mixture come to a boil.
Divide white hot chocolate between 4 mugs and top with whipped cream, mini marshmallows, and additional rose petals.