Step 1: Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Step 2: In a large bowl, toss the cubed butternut squash and halved Brussels sprouts with olive oil, smoked paprika, cumin, maple syrup, salt, and pepper until evenly coated.
Step 3: Spread the vegetables in a single layer on the prepared baking sheet and roast for 25-30 minutes, or until the squash is tender and the sprouts are charred.
Step 4: While the vegetables roast, whisk together the Greek yogurt, lime juice, and chipotle powder in a small bowl to create the crema.
Step 5: Warm the tortillas in a dry skillet or over an open flame until pliable and slightly charred.
Step 6: Assemble the tacos by filling each tortilla with the roasted vegetable mixture, drizzling with crema, and topping with pepitas, cilantro, and pickled onions.