Prepare Roasted Garlic, set aside. Prepare lentil puree, set aside.
In a large skillet, heat 1 tablespoon oil over low heat. Add carrot,squash, zucchini and leek; cook 7 minutes or until vegetables are tender.
In large bowl, mix together sauteed vegetables, grated potatoes, lentil puree, thyme, 3/4 teaspoon salt, and the pepper until well blended.
Heat oven to 200°. In 6" skillet, heat 1/4 inch oil over medium heat. Drop 1 heaping cup of vegetable- potato mixture into oil and flatten with a slotted pancake turner or spatula to make rosti.
Cook rosti until golden - about 10 minutes on one side. Cover skillet with inverted plate; invert rosti onto plate and slide back into skillet. Cook other side until crisp and golden - about 10 more minutes. Transfer rosti to wire rack on baking sheet; keep warm in oven while preparing remaining three rostis.
While rostis are cooking, prepare Carrot sauce: keep sauce warm over low heat. While last rosti is frying, in large skillet, heat about 1 teaspoon oil over medium heat. Add spinach and cook just until wilted - about 2 minutes. Toss with remaining 1/4 teaspoon salt.
To serve, pour about 1/4 cup carrot sauce onto each plate; place a rosti on top. Divide spinach and remaining roasted garlic cloves even among rostis.
Roasted Garlic: Heat oven to 375. With sharp knife, cut off tops of 2 large heads garlic. Peel some of loose outer skins from garlic. Place garlic heads on small baking sheet and brush with about 2 teaspoons olive oil. Bake garlic 35-40 minute or until very tender. When cool enough to handle, break cloves from heads of garlic and squeeze from skin. With fork or back of spoon, mash enough cloves to make 1/4 cup; set aside for use in carrot sauce. Set aside remaining roasted garlic cloves for garnish.
Lentil Puree: In medium size skillet, heat 1 teaspoon olive oil; add 1/2 cup finely chopped onion and saute until tender. Add 1/4 cup red lentils, 1 bay leaf and 1 cup water. Cover and cook 20 minutes or until lentils are soft. Remove bay leaf and drain. Mash lentils to make thick puree. Set aside to cool.
Carrot Sauce: In 2 quart saucepan, heat 2 cups carrot juice over medium heat to boiling. Cook until reduced by half - about 25 minutes. Add 1/4 cup mashed garlic (from roasted garlic), 2 tablespoons fresh lemon juice, and 1 tablespoon olive oil. In food processor fitted with chopping blade or blender at high speed, process or blend carrot mixture until well mixed. Strain mixture, reserving sauce only, in saucepan; keep warm.