Preheat oven to 425°F, line baking sheet with parchment
Trim Brussels sprouts, remove damaged leaves, halve lengthwise
Toss sprouts in bowl with olive oil, salt, pepper, garlic powder
Arrange cut side down in single layer on baking sheet
Roast 20-25 minutes, flipping halfway, until golden and crispy
While roasting, melt butter in small saucepan
Whisk in honey, balsamic vinegar, garlic powder, red pepper flakes
Cook bacon until crispy, drain, crumble
Transfer roasted sprouts to serving bowl
Drizzle with warm glaze, toss to coat
Top with crumbled bacon and Parmesan if using
Garnish with parsley, serve immediately