Mix 1 tablespoon balsamic vinegar, oil, salt, and black pepper together.
Pour the mixture onto the brussels sprouts and mix well.
In an oven safe pan lay the brussels sprout out so they are not overly crowded. Hence, each piece should be touching the bottom of the pan (even if it is just the tip).
Roast the brussels sprout in the oven for about 12 minutes.
Remove the pan from the oven.
Pour the remaining tablespoon of balsamic vinegar over the brussels sprouts and toss/mix with a spatula.
Be sure to spread the brussels sprouts out after mixing so each piece is touching the bottom of the pan.
Roast for an additional 10-15 minutes. Timing varies based on how big or small the pieces were. I normally cook for at least 25 minutes total regardless.
Remove from the oven.
Serve hot and crispy topped with parmesan cheese (optional).