Use a 2 quart saucepan over medium low to heat olive oil and blend in flour. Add the reserved liquids from shrimp and crap, stir well. Stir in cubed cream cheese, salt, garlic and horseradish. Stir until smooth. Add Asiago and Parmesan cheeses and stir until smooth. When the sauce is smooth, add shrimp and crab, blending well. Let simmer until thoroughly heated. Finally, add cream a little at a time until the seafood sauce starts to simmer and begins to resemble warm pudding. Let simmer for 12-15 minutes. Stir constantly so that it will not scorch on bottom. In a 9" baking dish coated with nonstick spray, place drained marinara sauce and carefully spoon seafood sauce on top. Sprinkle with frenshly shredded Parmesan cheese and bake in the preheated oven for 10-15 minutes until heated through. Do not brown. Serve with crusty breads.