Pre-heat oven to 400 degrees and line two baking sheets with foil.
Add Brussels to a large bowl and toss with olive oil, salt and pepper. Spread in a single layer between both pans and roast until brown and caramelized, about 40 minutes, moving the Brussels around with a spatula once about halfway through.
While the Brussels are roasting, sauté bacon slices in a frying pan until crispy. Reserve on a plate lined with paper towel.
Remove roasted Brussels from the oven and place in a large serving platter. Sprinkle cooked bacon and lemon juice on top to serve. Garnish with fresh parsley.