Make the dough: Set aside 1/2 cup of flour. In a large bowl, add 2 1/4 cups flour, sugar, salt, and yeast. Whisk or stir together until evenly dispersed. Set aside.
Heat the water, milk, and butter together in the microwave until mixture reaches 115-120°F. Stir the butter mixture into the flour mixture. Add the egg and only enough of the reserved flour to make a soft dough. Dough will be ready when it gently pulls away from the side of the bowl and has an elastic consistency.
On a lightly floured surface, knead the dough for about 3-4 minutes. Place in a lightly greased bowl and let rest for about 10 minutes.
Meanwhile, make the filling: Combine the cinnamon, sugar, graham cracker crumbs, and chocolate chips. Set aside.
After the dough has sat for 10 minutes, roll it out into a 14x8-inch rectangle on a lightly floured surface. Spread the softened butter on top. Sprinkle the cinnamon/graham filling all over. Roll up the dough tightly. Cut into 11 even pieces and place in a lightly greased 9-inch round pan or pie dish.
Loosely cover the rolls with aluminum foil and allow to rise in a warm, draft-free place for 60-90 minutes.
After the rolls have doubled in size, preheat the oven to 375°F. Bake for 25-30 minutes until lightly browned. Cover the rolls with aluminum foil after 15 minutes to avoid too much browning.
Make the frosting: Right before serving, top your sweet rolls with the marshmallow frosting. Using a handheld or stand mixer fitted with a paddle attachment, beat the softened butter and marshmallow creme on medium-high speed until smooth. Add the vanilla, cream, and confectioners' sugar and beat on medium-high until creamy and smooth. Frost warm rolls and sprinkle with chocolate chips, if desired. Using a knife, swirl the chocolate chips on top with the marshmallow frosting so they combine and have a swirled look.
Rolls are best enjoyed the same day, but will remain fresh covered tightly for up to 4 days in the refrigerator.