Trim the ends off the carrots and halve crosswise. Halve the carrots lengthwise, then cut lengthwise again in half or thirds, depending on the size, to create equal-size sticks.
In a mixing bowl, toss together the carrots, olive oil, pepper, garlic powder, salt and thyme. Transfer to a baking sheet and spread into a single layer. Bake, flipping halfway through, until the carrots are cooked through and the edges begin to crisp, 18 to 20 minutes.
Meanwhile, mix together the ketchup and ranch in a small bowl. Serve the carrot fries with the ketchupy ranch.