Preheat oven to 350°F (177°C) and grease a 9x13-inch baking dish with nonstick cooking spray or 1 tablespoon of softened butter.

Open the two cans of cinnamon rolls, set the icing containers aside, and place cold dough rolls onto a clean cutting board.

Cut each cinnamon roll into four equal quarter pieces using a sharp chef knife or bench scraper.

Spread the quartered dough pieces evenly across the bottom of the prepared 9x13-inch baking dish, leaving small spaces between pieces.

In a medium mixing bowl, whisk together the eggs, heavy whipping cream, whole milk, melted butter, light brown sugar, ground cinnamon, pure vanilla extract, and fine sea salt until smooth.

Slowly pour the sweet cream custard mixture around and between the dough quarters in the baking dish, avoiding pouring directly over top of the dough.

Place the baking dish on the center rack of the preheated oven and bake uncovered for 32 to 35 minutes.

Check for doneness when the tops are deep golden brown and an instant-read thermometer inserted into the center dough piece reads 195°F.

Remove the baking dish from the oven and let rest on a wire cooling rack for 10 minutes to allow the custard to set.

Warm the reserved icing containers in the microwave for 10 seconds, then drizzle evenly over the top of the warm casserole before serving.