Line a rimmed baking sheet with parchment paper and set nearby. Pour the crispy rice cereal into a large heatproof mixing bowl so it's ready when the marshmallow mixture is done.
In a large saucepan over low heat, melt the butter until it becomes fragrant and fully liquid — about 1 to 2 minutes. Keep the heat low so it doesn't brown.
Add the mini marshmallows and the pinch of salt to the melted butter. Stir constantly with a heatproof spatula until the marshmallows are completely melted and smooth, about 3 to 4 minutes.
Remove the pan from the heat and immediately stir in the vanilla extract. Add the orange food coloring a drop at a time and mix until you reach a vibrant pumpkin hue.
Pour the marshmallow mixture evenly over the bowl of cereal. Using the spatula, fold the cereal into the marshmallow in several quick strokes until the cereal is thoroughly coated. Work briskly — the mixture sets as it cools.
Let the mixture cool off the heat for 4 to 5 minutes so it’s safe to handle but still pliable.
Lightly spray your hands with nonstick cooking spray (or rub with a little butter). Scoop approximately 1/3 cup of mixture for each pumpkin, roll into a tight ball, then gently press to form a slightly flattened sphere.
To create pumpkin ridges, press shallow grooves around each ball with the back of a fork, the handle of a wooden spoon, or your fingers so it looks like a miniature pumpkin.
Soften a Tootsie Roll in the microwave for 3 to 4 seconds, then roll it between your palms into a short stub to serve as a stem. Insert one stem into the top center of each pumpkin. Place finished pumpkins on the prepared sheet.
Chill the pumpkins in the refrigerator for 10 to 15 minutes to firm up before serving. Store leftovers in an airtight container at room temperature for up to 3 days.