Preheat your oven to 500 degrees F. Line a large half sheet pan (or two baking sheets) with foil and lightly spray the foil with cooking spray. Set aside.
Trim the bottom 2 inches off the broccolini stems and cut any thick stems in half. Place the broccolini on the greased foil. Drizzle the broccolini with olive oil and sprinkle with salt and pepper. Add the garlic and toss until evenly coated. Lay the broccolini in a single layer.
Roast for 12 minutes. Carefully remove the pan from the oven and evenly space the cubed butter on the broccolini. Return to the oven and bake an additional 3 minutes or until broccolini reaches your desired crisp-tenderness. (You can even broil if desired for a few minutes.)
Remove the broccolini from the oven and toss with lemon juice. (I like to use a full 2 tablespoons.) Season with additional salt and pepper to taste and sprinkle with garlic from the before serving warm.