Preheat oven to 425 degrees F.
Coarsely grind caraway seeds with salt in an electric coffee/spice grinder or crush with a rolling pin. Mince garlic, then mash to a paste with salt mixture using flat side of a chef's knife. Transfer paste to a large bowl and whisk in honey, lemon juice, oil, spices, and pepper.
Put zucchini, turnips, bell peppers, butternut squash, and onions in an oiled large roasting pan, then add half of spice mixture and toss until well coated. Stir tomatoes and broth into vegetables. Add hens to large bowl with remaining spice mixture and toss to coat, then arrange hens, breast sides up, over vegetables in pan.
Cover pan tightly with foil and roast in middle of oven 1 hour. Uncover and roast until hens are browned and vegetables are tender, 20 to 30 minutes more. Skim fat from cooking liquid. Sprinkle herbs on top and spoon some cooking liquid over hens.
Serve with couscous, if desired.