In a large pot, melt the butter over low heat.
Add the marshmallows and stir until completely melted and combined with the butter.
Remove from the heat. Add several drops of yellow food coloring, mix it together, then add red food coloring one drop at a time, mixing as you go. Add red/yellow drops until you reach your desired color. (I used about 4 drops red and 12 drops yellow). Mix well.
Add the Rice Krispies and stir to combine.
Coat both sides of your hands with a generous amount of cooking oil, and roll the Rice Krispie mixture into small balls. Set on parchment paper. Add oil to your hands after each ball.
While the balls are still warm, gently press a Mini Rolo into the top of each pumpkin for the stem and add a green M&M beside it as the leaf. (Tip: If the pumpkins cool before you're finished, use the end of a thick marker or apple corer to make a small indent in the top for the chocolate to sit in.)
Allow to cool until firm.