Even the most unpopular vegetables (I'm talking to you, cauliflower) come out amazing when they're roasted. But one mistake people make when roasting vegetables is starting them in a cold pan instead of preheating the pan first.
It's a lot easier to just dump the prepped veggies in the pan and stick it in the oven, but Splendid Table notes:
it's something that a lot of us don't even think to do, while oddly we're all very aware of how important it is to preheat your pan on the stovetop before you add things in. The same principle applies here: When you preheat your pan for roasted vegetables, you're going to end up with less sticking and better browning.
This is particularly important with tender spring and summer vegetables -- if you start them in a cold pan, it's going to take that much longer in the oven while they roast for them to cook. You're probably going to end up with mushy vegetables that don't get much browning.
But if you preheat the pan and you lightly coat your veggies in oil, the minute they hit the pan you're going to hear that sizzle just like you should when you sauté them.
Hit up the link below for more cooking rules you might not be following, such as starting potatoes in cold water, rather than dumping them in when the water's boiling.
The correct way to slice an onion: 5 cooking rules explained [The Splendid Table]