Gelatin Pinwheel / Fruity Roll-Ups

From : http://www.joyofjello.com/?p=1085
Ingredients
1 (3 oz.) pkg. jello
1/2 cup water
1 1/2 cups miniature marshmallows



Method : 
Lightly spray an 8 or 9 inch pan square pan with non-stick cooking spray and make sure it is spread well.

Stir together water and jello powder in a glass bowl and microwave for 1 minute.   Remove bowl and stir well making sure jello is dissolved.  If necessary, return to microwave for 20 seconds or so to make sure jello is dissolved and stir again.

Add marshmallows and return to microwave for 20-40 seconds or until marshmallows have just begun to puff.  This is the key to a successful marshmallow layer!  If you over cook the marshmallows, they just dissolve and your roll-up will not have two distinct layers.

Whisk quickly until marshmallows are dissolved.

Pour quickly into prepared pan and chill in fridge for 45 minutes or until well set.  Creamy layer will float to the top.

Remove the pan from fridge.  At this point,  the jello should be very firm and easy to handle.  Gently pull one side away from pan and lift entire sheet onto counter.  Starting at one end, roll up tightly.  With seam side down, cut into 10-12 (1/2) inch slices.  We found it easiest to cut with a piece of thread or dental floss.  Just put the string around roll-up, cross and pull.

Serve immediately or refrigerate until ready to serve.