Lightly spray an 8x8 baking pan with nonstick spray. You can use your fingers to evenly rub the spray over the bottom and sides of the pan as you do not want to overspray the pan, or your jello roll ups will be greasy.

To a medium, microwave-safe mixing bowl, add the boiling water and flavored jello gelatin. Whisk to fully dissolve the gelatin.

To the bowl of gelatin, add the mini marshmallows and stir to coat all the mini marshmallows in the gelatin.

Heat the bowl of flavored gelatin and mini marshmallows for 30 seconds in the microwave on high heat. Remove the bowl from the microwave and whisk until all the mini marshmallows have dissolved into the gelatin and the mixture looks light and frothy.

Pour the mixture into the prepared 8x8 pan.

Refrigerate the pan of jello roll ups for a minimum of 1 hour or until the gelatin has firmly set.

Carefully run a butter knife around the edges of the pan to loosen the jello from the edges. Gently pull up one corner of the sheet of firmed Jello roll up and pull to lift the sheet of jello out of the pan. Place the sheet of jello roll up onto a sheet of parchment paper, fluffy marshmallow side up so that it is ready to roll up and slice. Be sure that your parchment paper is slightly larger than the pan of Jello roll ups.

Starting at one end of the Jello square, gently roll the jello into a spiral until you have a log.

With the seam side down of the Jello roll up, slice the log into 12 (approximately ½ inch) slices. Be sure to use a sharp knife to get nice, clean slices.

Transfer the Jello roll ups to a plate and serve.