Preheat the oven to 400º and line a baking sheet with parchment paper. Lay the rainbow carrots on the baking sheet and drizzle the olive oil. Toss the carrots on the parchment paper to evenly coat them with the oil.
Sprinkle the carrots with salt and pepper, then place in the oven to roast for 25-28 minutes, or until fork tender.
Meanwhile, peel and mince (very finely chop) the garlic cloves.
In a small sauce pan, melt the butter on a medium heat, then add in the minced garlic. Let simmer for 5-7 minutes on a low flame. Once the carrots finished roasting, pour the garlic butter on top of the carrots, and top with fresh thyme.
Notes
When making the garlic butter sauce, keep the flame on a consistent medium to medium-low heat, depending on your stove. You don't want the butter to burn or the garlic to char.Use enough olive oil to coat the carrots well. The oil helps the carrots caramelize and soften when they roast.