Make the chutney: Combine 1 1/2 cups cilantro, the coconut, serrano, ginger, garlic, 1 teaspoon curry powder, 2 tablespoons lime juice, 1/4 cup coconut oil, 1/2 teaspoon salt and 2 tablespoons water in a food processor. Pulse until smooth, scraping down the bowl as necessary. Pulse in 1 to 2 more tablespoons water if the chutney is too thick.
Preheat a grill to medium high. In a small bowl, combine the remaining 1 tablespoon coconut oil and 1 teaspoon curry powder, and 1/2 teaspoon salt. Rub all over the halibut fillets. Lightly oil the grill with coconut oil. Grill the halibut until well-marked and the fish flakes easily with a fork, 3 to 4 minutes per side. Remove to a plate. Grill the rolls until charred in spots, 30 seconds to 1 minute per side.
Mix the carrots and remaining 1 tablespoon lime juice and 1/4 cup cilantro in a medium bowl. Season with 1/4 teaspoon salt.
Spread the cilantro chutney on the cut sides of the rolls. (If the chutney is dry, mix in 1 to 2 more teaspoons coconut oil.) Fill the rolls with the carrot mixture and halibut. Serve with sweet potato chips.