For the crepes: in a food processor or blender, combine eggs, milk, beer, salt, and flour and process until mixture is smooth, approximately 2 minutes. Cover and referigerate for at least 2 hours.
Using melted butter or vegetable oil, lubricate a 10-inch, nonstick pan and heat to medium-hot. Pour 2 ounces of batter in the pan and swirl until bottom of pan is covered. Cook until the top appears dry and the bottom has begun to brown. Turn and brown the other side lightly. Stack with a piece of waxed paper between each. Repeat with rest of the batter. For the oysters: melt the butter in large saute pan. Add flour and stir constantly until butter and flour are bubbling. Add the half-and-half, stirring constantly. Add the sage leaves, and stir in the tomato paste. Add the oysters and their liquor, and cook for about 2 minutes. Add salt and cayenne, to taste. Add green onions, prosciutto, and grated cheese. Gently fold in the fresh tomatoes. Filling should be quite thick (if too thick, add more cream or oyster liquor).
Preheat the oven to 350 degrees F. Arrange 1 crepe on a flat surface, add about 1/4 cup of oyster mixture to bottom end of crepe and roll. Place crepe seam side down in buttered baking dish. Continue with rest of crepes, spoon some of the sauce on top of the crepes.
Bake in preheated oven for approximately 15 minutes until hot. Garnish as desired.