Preheat the oven to 400 degrees.
In a bowl big enough to hold the carrots, mix the olive oil, mustard, and thyme.
Add the carrots and toss to coat.
Add the sliced lemons, and toss.
Spread the carrots and lemons on a baking sheet, and sprinkle with salt and fresh-ground pepper.
Toss the carrots around a little, and sprinkle with a little more salt and pepper.
Roast for about 15 minutes.
Stir up the carrots, making sure to flip the lemon slices.
Roast about 8-10 more minutes; the carrots should be tender and golden.
Sprinkle with the chopped parsley.
Remove from the oven, arrange on a serving dish, and squeeze some fresh lemon over the top.
This is a beautiful and zesty side dish that will complement almost any main dish!