Make sure you use a vegetarian-friendly hard cheese if you’re cooking for vegetarians.
Adding pasta cooking water to the vegetables is an easy way to create a sauce as the starch in the water acts as a binder.
When roasting the vegetables, they don’t need to be fully roasted before adding the pasta, just golden as directed in the recipe. You don’t want fully charred edges as they will cook further after adding the pasta and could burn and become bitter.