Preheat oven to 350 degrees.
Coat two jellyroll pans with cooking spray.
Line with wax paper and coat with cooking spray.
Set aside.
Beat eggs in a large mixing bowl with an electric mixer for 5 minutes.
Add water and beat at low speed until blended.
Gradually add cake mix, beating at low speed until moistened.
Beat at medium high speed 2 minutes.
Divide batter in half and spread evenly into prepared pans.
Bake each cake one at a time for 13 minutes or until done.
Spread a two cloth towels on counter and sprinkle with cocoa.
When cakes are done, immediately loosen from pan and turn onto prepared towel.
Peel off wax paper.
Starting at narrow end, roll up each cake and towel together.
Place seam sides down on wire rack.
Cool completely.
Beat whipping cream until soft peaks form.
Fold in 2 T mint liqueur.
Unroll cake rolls and sprinkle with remaining liqueur.
Spread each cake roll with half of whipped cream mixture.
Reroll cakes without towels and place seam side down on a baking sheet.
Cover and freeze at least 1 hour.
Dust with additional cocoa and garnish as desired.
Heat half and half in heavy saucepan over low heat.
Stir in chocolate chips, marshmallows, and salt.
Cook until melted and smooth.
Remove from heat and stir in liqueur. Cool.
Drizzle over cake roll.
May be frozen without sauce for up to 3 months.