Preheat the oven to 400°F. Line two baking sheets with parchment paper. Set aside.

In a large bowl, toss the carrots with olive oil, salt, and ground black pepper until evenly coated. Arrange in an even layer on one of the baking sheets. Roast for 15 minutes, just until fork-tender.

On a floured surface, roll out the puff pastry sheet into a 12-inch x 10-inch rectangle. Fold over the edges about 1/2-inch on each side to form a border all around. Use a fork to lightly prick all around the area inside the border. Bake for 10 minutes. If the dough puffs up in the middle, use your fork to gently press it back down, leaving the border defined.

Gently spread the softened Boursin cheese to cover the pastry inside the border. Don't worry if the cheese doesn't spread evenly; it will soften during the second baking time.

Arrange the roasted carrots over the cheese layer and return to the oven. Bake for an additional 10 minutes, until the edges are golden.

Cool for 10 minutes then sprinkle with parsley and dill. Slice and serve warm or at room temperature.