1) Turn your oven up to high heat. Roast your brussel sprouts at 450. Lower heat tends to cause soggy sprouts. 2) Avoid using a silicone baking mat on your sheet pan. I love my silicone baking mat but I’ve found that it doesn’t crisp up vegetables very well so I’d recommend using parchment paper or tinfoil on your baking sheet instead. 3) Do not overcrowd your sheet pan. If you plan on doubling the recipe be sure to split between two sheet pans otherwise they will be overcrowded and will not crisp up. 4) Be sure to dry your brussel sprouts after boiling. Removing any excess water will ensure they get crispy.