Preheat oven to 400 degrees. Line a sheet pan with foil and coat the foil with cooking spray. Place the brussels sprouts on the pan in a single layer. Drizzle the olive oil over the brussels sprouts and season them generously with salt and pepper. Toss to coat evenly.
Bake for 20-30 minutes or until brussels sprouts are tender and beginning to caramelize.
Add the butter onto the hot pan and stir the brussels sprouts around until they're coated in the butter. Transfer to a serving platter and top with pecans and pomegranate seeds. Serve immediately.
Make Ahead: The brussels sprouts can be trimmed and halved up to 2 days in advance.