Line 13x9 pan with parchment or wax paper. Melt chocolate chips, butter and condensed milk in a medium to large pan over medium/low heat, stirring constantly to keep it from scorching.
Once melted, remove chocolate mixture from heat and allow to cool slightly. Stir peanuts and marshmallows into chocolate mixture.
Spread rocky road mixture into prepared pan and add sprinkles and/or candy decorations as desired. Chill until set, approximately 2 - 3 hours. Cut into squares and serve.