How to Make It
Preheat oven to 350°F. Prepare cake batter according to package directions. Divide batter among 24 muffin cups lined with paper baking cups. Bake until a wooden pick inserted in center comes out clean, 14 to 19 minutes. Cool cupcakes in pans on a wire rack 10 minutes. Remove cupcakes to racks, and cool completely, about 30 minutes.
Prepare Rose-Vanilla Buttercream.
Spoon Rose-Vanilla Buttercream into a piping bag fitted with a large star tip; pipe onto cooled cupcakes. Gently press an edible rose petal into the side of each cupcake.