Bring a large pot of salted water to a boil. Add pasta and cook until tender but still al dente, about 8 minutes or according to package directions. Meanwhile, in a large skillet heat oil. Add garlic, paprika, thyme, cayenne and bell peppers and saute for a minute. Then add white wine, cover and simmer over low heat until the peppers are almost tender, about 3 minutes. Add shrimp and oysters, cover and simmer until shrimp are cooked through, another 2 minutes. Uncover skillet, add chicken broth and cook until broth has reduced slightly, about 1 minute. Remove skillet from heat, swirl in butter and adjust seasoning. Drain pasta and return to pot, off the heat. Add the shrimp mixture and toss well with pasta. Serve out portions and garnish with parsley or scallions.