Put a large rimmed sheet pan in the oven and heat the oven to 425°F.
Trim the stem ends of the Brussels sprouts, remove any yellow outer leaves and cut each sprout in half. Quarter very large ones.
Toss the sprouts with the olive oil, salt and pepper.
Spread the sprouts on the hot pan, cut side down, in one layer (use two pans if they overlap). Roast for 20 to 25 minutes, until the cut sides are deep brown and a knife slides easily into the thickest one.
Meanwhile, cook the chopped bacon in a skillet over medium heat for 7 to 9 minutes, until crisp. Drain on a paper towel and leave about 1 tablespoon of fat in the skillet.
Add the balsamic vinegar and honey to the skillet and simmer over low heat for 1 to 2 minutes, stirring, until slightly syrupy.
Toss the hot sprouts with the glaze and bacon in a serving bowl. Top with Parmesan if you like and serve right away.