Shrimp and Roasted Fennel Ditalini

Heat oven to 450°F. Shell shrimp, but keep tails intact, if desired; reserve shells. In a small pan over medium heat, toast fennel seeds until golden brown, 5 minutes; crush. In a bowl, toss shrimp with fennel seeds. In same pan, bring 1 cup water to a boil with 1/2 teaspoon salt and reserved shells; reduce heat and simmer, partially covered, 30 minutes. Remove and discard shells; simmer until stock reduces by half, 5 minutes. In a roasting pan, place sliced fennel, garlic, oil, pepper and remaining 1/2 teaspoon salt; toss. Roast until fennel is tender, 20 minutes. Stir in shrimp, stock and zest; roast until shrimp are just cooked through, 5 minutes. Cook pasta as directed on package until al dente. Drain pasta, reserving 1 cup cooking liquid. Add pasta to roasting pan; roast until pasta is completely cooked, adding reserved liquid a little at a time and stirring to reach desired consistency, 5 to 10 minutes. Serve garnished with julienned zest and fennel fronds, if desired.