Preheat oven to 375°.: The kitchen fills with a faint warm dry heat that sets the stage for browning, and preheating to 375° ensures the vegetables cook through evenly while developing caramelized edges. You should feel steady oven warmth and, if your oven has hot spots, rotate the baking sheet halfway through cooking. A common mistake is placing cold pans into a cold oven which prolongs cook time and prevents crisping, so always let the oven fully reach temperature before you start.
Place cut vegetables into a skillet or onto a baking sheet.: At this point you will notice the contrast between the glossy sliced red onion , the vivid green of the halved brussels sprouts , and the orange of the halved or diced carrots . Arrange them in a single layer so air circulates and edges can brown. If you overcrowd the pan the vegetables will steam rather than roast, which leads to limp textures, so use two pans if needed to maintain space.
In a small bowl mix together the maple syrup, smoked paprika, cayenne pepper, and oil. Pour the mixture over the vegetables, and toss to coat.: You will smell the sweet maple and the smoky spice as you whisk them together, and the glossy coating should cling to each piece. Tossing ensures even distribution so each bite has balanced flavor. A sticky syrup can clump if added cold, so make sure the oil and spices are well combined; if the glaze pools, spread it with your hands or a spatula to achieve an even coating.
Sprinkle salt over the vegetables, and roast for 40-45 minutes, or until the vegetables are tender.: As the vegetables roast the aroma evolves into a toasty, savory scent and you will notice edges turning golden to deep brown. The brussels sprouts should yield to a fork and the carrots should be tender but still hold shape. If you take them out too early they will be crunchy in the center, and if you leave them much longer they can dry out, so test for tenderness around the 40 minute mark.
Check your vegetables 30 minutes into the cook time, and stir them if necessary.: When you stir you will hear a soft scraping and see juices recoat the vegetables, promoting even browning on all sides. This is a chance to move browned pieces toward the center for more even heat exposure. Avoid stirring too often as that cools the pan and prevents crisp edges, but failing to check can leave some pieces overcooked while others are underdone.
Serve hot and garnished with toasted pumpkin seeds.: The final sensory moment is the crack of toasted seeds and the warm, slightly sticky glaze on the vegetables. Scatter the toasted pumpkin seeds right before serving so they stay crunchy. A common oversight is adding seeds too early, which causes them to lose their crispness, so always garnish at the last minute.