Rub off excess papery skin from garlic heads without separating cloves, and slice about 1/2 inch off the top. Place each head on a square of foil (cut-end up). Sprinkle each with 1 tablespoon of water and pinch the edges of the foil together to make a package. Roast until cloves are very soft, 40 to 50 minutes. Unwrap and let cool slightly. Squeeze cloves out of skins into a small bowl; set aside.
Heat oil in a saucepan over low heat. Add shallot and cook until softened, 1 to 2 minutes. Add marjoram and crushed red pepper; cook until aromatic, about 30 seconds. Add wine and bring to a boil. Increase heat to medium-high and cook until mixture has reduced to 1/4 cup, 10 to 14 minutes. (The wine will be nearly evaporated.) Reduce heat to low; add reserved clam juice and roasted garlic and whisk until smooth. Stir in clams and 1/4 cup parsley; heat gently over low heat. Keep sauce warm.
Cook pasta in a large pot of boiling salted water until just tender, 8 to 10 minutes or according to package directions.
Meanwhile, make gremolata: combine 1/4 cup parsley, lemon zest and garlic clove; mix well.
Drain the pasta and transfer to a large, warm serving bowl. Stir lemon juice and butter into clam sauce, and pour over pasta. Toss gently, then sprinkle the gremolata over the top. Serve immediately, with lemon wedges.
Per serving :
4 g Fat;
1 g Sat;
1 g Mono;
15 mg Cholesterol;
48 g Carbohydrates;
14 g Protein;
8 g Fiber;
462 mg Sodium;
213 mg Potassium