Combine the marshmallows and butter in a large pot or Dutch oven over low heat. Cook, stirring often, until the mixture is melted and smooth. Remove from the heat and stir in a few drops of orange food coloring and vanilla extract.
Add the Rice Krispies and stir until coated. Let stand at least 15 minutes and until cool enough to handle.
With greased hands, shape the cereal mixture into pumpkin shapes. (I use an ice cream scoop for ease.) Let stand at room temperature or in the fridge until hardened. Use a skewer or paring knife to create indentions in the sides of the balls to mimic pumpkins, if desired.
Cut each chocolate mini Tootsie Roll in half for the stems. Roll out some of the green Tootsie Rolls with a rolling pin until flattened and cut out leaf shapes. Roll some green Tootsie Rolls into thin ropes to look like green curly stems. Decorate each top of the pumpkin with the Tootsie Roll stumps and leaves. Store in an airtight container until ready to serve.