Preheat oven to 425°F. If you want maximum browning, put your rimmed baking sheet in the oven while it preheats. Cut broccoli — stalk included — into coins and florets roughly 1½–2 inches across; uniform sizing means even cooking. Line the hot pan with foil or parchment. Toss broccoli with about 2 tablespoons olive oil per 1–1½ lbs, season well with kosher salt and black pepper, and add smashed garlic if using. Spread in a single layer with no pieces touching — crowding steams instead of roasts.

Place the baking sheet on the center rack of your preheated 425°F oven. If the pan was preheated, transfer the broccoli carefully onto the hot surface to jump-start browning. Roast 18–24 minutes. At the 10-minute mark, check the undersides. Flip or toss with a metal spatula for even browning, or leave undisturbed for one deeply caramelized side. Look for deep golden-brown edges, crispy floret tips, and stems that are crisp-tender when pierced with a fork. Do not use convection — it over-dries the broccoli. If edges are browned but stems are still firm, pull the pan, cover tightly with foil, and rest 5–10 minutes; the steam will finish the stems without losing the browning.

Pull the broccoli when florets are deeply browned at the edges and stems yield to a fork with a little bite. Season immediately with salt while hot. Add Parmesan, a squeeze of lemon juice, and red pepper flakes if desired. Serve straight off the pan — it loses crispness fast. Avoid crowding the pan, low heat, and wet florets before roasting.