Before starting, place the bag of mini marshmallows in the freezer for at least 5 minutes. This keeps the marshmallows from melting too fast.
Place a large pan over medium-low to medium heat. Add the butter, peanut butter, and chocolate. Melt and blend the ingredients stirring often.
Remove the pan from the stove and let cool for about 5 minutes.
While the chocolate mixture is cooling, prepare an 8 x 8-inch or 9 x 9-inch pan by lining it with parchment paper. This is so you can lift the bars out of the pan easily when you are ready to cut them.
When the chocolate has cooled for about 5 minutes, stir in the crispy rice cereal and 3 cups of mini marshmallows. Stir quickly and just enough to keep the mini marshmallows from completely melting.
Pour the rocky road bars mixture into the prepared dish. Spread evenly and top with the remaining marshmallows.
Refrigerate the bars until fully set, about 2-3 hours.
Lift the whole chocolate out of the pan. Cut the rocky road into squares or bars. Serve and enjoy!
Notes
Store any leftover bars in a covered container, in the refrigerator, for 3 to 4 days. You can easily double this recipe for a larger crowd.