Make the lobster butter: In small bowl, add the lobster roe and macerate with a whisk. Add 2 tablespoons butter and emulsify the roe with the butter.
Make the breadcrumbs: Heat 4 tablespoons butter in a medium skillet over medium heat until melted and foamy, about 1 minute. Stir in the breadcrumbs and cook, stirring often, until golden brown, about 4 minutes. Season with salt and pepper to taste and set aside.
Make a bechamel: In a medium saucepan, heat the milk and heavy cream.
In a large saucepan, melt the remaining 6 tablespoons butter over medium heat. Add the rosemary and saute until fragrant, 2 to 3 minutes. Add the flour and cook, stirring constantly, until it forms a light golden paste (make sure it doesn't brown), 5 to 6 minutes. Add the warm milk and cream and whisk until incorporated. Bring to a simmer and cook, stirring occasionally, until the mixture is thickened and coats the back of a spoon, about 15 minutes. Add the cheeses and whisk while the bechamel cooks, but do not let it boil. Cook until the cheeses are melted, then remove from the heat and season to taste with salt.
Add the lobster butter and truffle butter to the bechamel and stir to fully incorporate. Add the cooked pasta and lobster meat and stir gently to combine. Transfer to a 9-by-13-inch baking dish and sprinkle with the breadcrumbs. Bake until heated through and bubbling around the edges, about 20 minutes.
Lobster roe can be found in female lobster bodies or bought from specialty seafood markets.