Preheat your oven to 375°F (190°C).
Peel the bananas and slice them in half lengthwise.
In a small saucepan, melt the unsalted butter over medium heat. Add the vanilla beans and cinnamon sticks and let them infuse the butter for about 5 minutes.
Add the dark rum to the saucepan and simmer for another 3 minutes to combine the flavors.
Arrange the banana halves in a roasting dish, then pour the spiced rum and butter mixture evenly over them.
Roast the bananas in the oven for 12-15 minutes until they are tender and caramelized.
Remove the vanilla beans and cinnamon sticks from the roasting dish.
Drizzle the warm roasted bananas generously with dulce de leche.
Serve immediately, optionally with a scoop of vanilla ice cream or whipped cream for a decadent dessert.