Preheat the oven to 400F. Melt the butter over medium-high heat. Add the hibiscus, onion, carrots, jicama, parsley, garlic, sugar, oregano, thyme and cumin. Season with salt to taste. Cook, stirring occasionally, until the vegetables are tender. Remove from the heat.
Rinse the diced sweet potatoes until water runs clear. Then drain very well in a strainer. Toss with the oil, 1 teaspoon salt and 1/2 teaspoon pepper. Place on an unlined sheet tray and roast until golden brown on the outside and soft on the inside, 15 to 18 minutes.
Mix the cooked hibiscus mixture and roasted sweet potatoes and gently warm in a skillet with a bit of vegetable stock or water.
Divide mixture between butter lettuce leaves and sprinkle with queso fresco, if desired.