Step 1: Lightly grease an 8×8 or 9×9 inch glass baking dish with non-stick spray and wipe away any excess with a paper towel.
Step 2: In a medium microwave-safe bowl, combine the flavored gelatin and boiling water. Whisk vigorously until the gelatin is completely dissolved.
Step 3: Add the mini marshmallows to the gelatin mixture. Do not stir yet.
Step 4: Place the bowl in the microwave and heat on high for 30-45 seconds, or until the marshmallows have puffed up significantly.
Step 5: Whisk the mixture until the marshmallows are completely melted and the liquid is smooth and frothy.
Step 6: Pour the mixture into the prepared baking dish. Place it on a level surface in the refrigerator for 45 to 60 minutes until fully set.
Step 7: Once set, use a spatula to loosen the edges of the gelatin. Carefully roll the gelatin sheet into a tight log.
Step 8: Use unflavored dental floss or a very sharp knife to slice the log into 1-inch thick jello roll ups.