Make the Key Lime Pie Filling
In a saucepan, whisk together the sweetened condensed milk, egg yolks, key lime juice, lime zest, and salt.
Cook over medium-low heat, stirring constantly for 9–12 minutes, or until the mixture reaches 175°F (79°C).
Transfer to a bowl and refrigerate until completely chilled.
Prepare the Tangzhong
In a small saucepan, whisk together the water and bread flour.
Cook over medium heat, whisking constantly for 4–5 minutes until a thick paste forms.
Transfer to a bowl and allow to cool slightly.
Make the Dough
In the bowl of a stand mixer, combine bread flour, sugar, yeast, and salt.
Add the heavy cream, milk, egg, vanilla bean paste, and prepared tangzhong.
Knead with a dough hook on low speed for 2 minutes until a rough dough forms.
Add softened butter one tablespoon at a time while mixing.
Continue kneading for 8–10 minutes until the dough is smooth and elastic.
Shape into a smooth ball and place back into the mixing bowl.
Cover and rest for 30 minutes.
Prepare the Filling
Mix together the brown sugar, softened butter, and cinnamon until smooth.
Line a 9×13-inch metal baking pan with parchment paper.
Arrange graham cracker sheets across the bottom of the pan, breaking pieces as needed to cover the entire surface.
Assemble the Rolls
Roll the dough into a 15×21-inch rectangle on a lightly floured surface.
Spread the cinnamon sugar filling evenly over the dough, leaving a 1/2-inch border along one long edge.
Spread 2/3 cup of chilled key lime filling over the cinnamon sugar layer.
Sprinkle with graham cracker crumbs.
Using a pizza cutter, cut the dough into twelve strips approximately 1¾ inches wide.
Roll each strip individually away from you and place each roll into the prepared pan.
Rise and Bake
Cover the pan with plastic wrap and let the rolls rise for 1–2 hours, or until doubled in size.
Preheat the oven to 325°F (162°C).
Bake for 30–40 minutes, or until the center rolls reach an internal temperature of 185°F (85°C).
Allow the rolls to cool slightly.
Make the Frosting
Beat the cream cheese and powdered sugar together until smooth.
Add the remaining key lime pie filling and mix until creamy and lump-free.
Finish and Serve
Spread the frosting generously over the warm rolls.
Sprinkle with additional graham cracker crumbs before serving.