When roasting vegetables, it is generally better to arrange them in a single layer on the pan rather than packing them tightly together to form a "roast." Here's why:
Even Cooking: Placing vegetables in a single layer allows hot air to circulate around each piece, promoting even cooking. When vegetables are tightly packed, they can end up steaming rather than roasting, leading to uneven results.
Browning and Caramelization: Roasting vegetables in a single layer provides more surface area exposed to direct heat. This enhances browning and caramelization, resulting in delicious flavor and texture. When vegetables are crowded, the moisture released can create steam, inhibiting browning.
Crispiness: If you desire crispy roasted vegetables, it's important to give them enough space. Crowded vegetables can trap moisture, preventing them from achieving the desired crispness.
Roasting Time: Roasting vegetables in a single layer generally requires less time because the heat can reach each piece more effectively. If you overcrowd the pan, the vegetables may take longer to cook, potentially resulting in overcooked or undercooked portions.
However, it's worth noting that some recipes or dishes may call for vegetables to be packed together tightly, such as when making a vegetable medley or roasted root vegetables. In such cases, it's important to adjust the cooking time and temperature accordingly and stir the vegetables occasionally to ensure even cooking.
Ultimately, for optimal results, it's generally recommended to arrange vegetables in a single layer, giving them space to roast and brown evenly.