Heat olive oil in a 2 quart saucepan over medium-low heat.

Blend in flour to create a roux.

Add the reserved liquids from the shrimp and crabmeat, stirring well to combine.

Incorporate cream cheese, salt, crushed garlic, and horseradish into the sauce, stirring until smooth.

Add Asiago and Parmesan cheeses, stirring until smooth and melted.

Incorporate the shrimp and crab meat.

Simmer until heated through.

Add half-and-half gradually, until the sauce starts to simmer and resembles a warm pudding.

Simmer the sauce for 12 minutes, stirring frequently to prevent scorching.

Spray a 9-inch shallow baking dish and spread the drained marinara sauce on the bottom.

Carefully spoon the seafood sauce on top of the marinara sauce.

Sprinkle with freshly shredded Parmesan cheese.

Bake in a preheated oven at 325°F for 10 minutes, or until heated through and lightly golden on top.