Arrange the Brussels sprouts and carrots on a baking sheet with the garlic. Add olive oil, salt and pepper, tossing to combine so the veggies are coated.
Roast for 25-30 minutes, tossing halfway through. Remove and transfer to a serving plate.
Notes
For easier cleanup, just place the veggies on some parchment paper.
You know the carrots are done when you can pierce the largest part of the carrot with a fork.
Speaking of doneness, you want to try to have similar diced vegetables so they all cook in about the same amount of time.
Don't overcrowd the pan or the veggies will steam instead of getting crispy.