Preheat oven to 425°F and line a large rimmed sheet pan.
Pat broccoli dry with towels so it roasts crisp.
Toss broccoli with olive oil and lemon juice in a big bowl.
Sprinkle ranch mix, garlic powder, onion powder, salt, pepper, and red pepper flakes; toss to coat.
Spread on the pan in a single layer, cut sides down if large.
Roast 15 minutes, then stir and scatter panko and half the Parmesan.
Roast 7 to 10 minutes more until edges are deeply browned.
Finish with remaining Parmesan and bacon, then serve immediately.