Raita: Preheat oven to 450°F. Cut top 1/2" off head of garlic; discard. Place garlic on a sheet of foil. Drizzle with oil; sprinkle with salt and pepper. Wrap in foil. Roast until tender, about 45 minutes. Let cool. Squeeze cloves from skins, keeping cloves intact. Stir cumin in a small dry skillet over medium heat until deep brown, 2-3 minutes. Let cool. Finely grind in a spice mill. Mix yogurt, cucumber, cilantro, mint, jalapeño, and 1/2 teaspoon lemon juice in a medium bowl. Stir in cumin. Season with salt, pepper, and more lemon juice, if desired. For lentil cakes: Rinse legumes; place in a medium bowl with rice. Add water to cover by 3". Let legumes and rice soak at room temperature for 3-5 hours. Drain legumes and rice; transfer to a food processor. Add garlic, ginger, and jalapeño. Process until grainy paste forms (add 1-2 tablespoons water if necessary). Transfer to a large bowl; mix in tendrils and next 6 ingredients. Heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Spoon 4 scant 1/4-cupfuls of batter into skillet, flattening with the back of a measuring cup into 1/4"-thick cakes. Reduce heat to medium; sauté until golden brown and cooked through, adding 1 more tablespoon oil when cakes are flipped, about 4-5 minutes per side. Repeat with remaining oil and batter. Divide raita among plates; top with a roasted garlic clove. Place 2 cakes on each plate.