Toss 1 pound carrots (cut into 2-inch pieces) and 1 halved shallot with vegetable oil and kosher salt on a baking sheet. Roast at 425 degrees F until tender, 25 minutes; let cool slightly. Transfer to a food processor; add 1/2 cup water, 1/4 cup white miso paste, 2 tablespoons chopped fresh ginger, 2 chopped scallions,2 tablespoons vegetable oil and 1 tablespoon each rice vinegar and soy sauce. Puree until smooth, then transfer to a bowl and top with sesame seeds and more scallions. Serve with rice crackers.