Preheat oven to 350°.
Place the sweet potatoes on a baking sheet. Bake at 350° for 1 hour and 25 minutes or until potatoes are tender. Cool slightly; peel.
Combine carrot, orange juice, and ginger in a small saucepan. Bring to a boil; reduce heat, and simmer for 15 minutes. Drain the carrot mixture in a colander over a bowl, reserving 3/4 cup cooking liquid. Combine potato and carrot mixture, and mash. Stir in 3/4 cup cooking liquid, butter, salt, and pineapple.