Preheat your oven to 400°F (200°C). Slice the zucchini, eggplant, red bell pepper, yellow bell pepper, and red onion into thin pieces. In a large bowl, toss the veggies with minced garlic, olive oil, dried thyme, dried oregano, salt, and pepper until evenly coated. Spread the colorful mixture on a baking sheet and roast for 20-25 minutes, or until tender and caramelized. Let the roasted vegetables cool down while you prepare the galette.

As the vegetables cool, roll out the thawed sheet of puff pastry on a piece of parchment paper until it forms a 12-inch circle. If the pastry gets too sticky or warm, rest it in the refrigerator for a few minutes.

Once the roasted vegetables have cooled, arrange them in the center of the pastry circle, leaving about a 2-inch border all around. Gently fold the edges of the pastry over the filling, pleating as you go to create a rustic look while leaving the center exposed.

Preheat the oven again to 400°F (200°C) and prepare for baking. Brush the edges of the pastry with the beaten egg to achieve that lovely, golden finish. Optionally, sprinkle some additional dried herbs or flaky salt on top for extra flavor.

Carefully transfer the assembled galette (still on the parchment paper) onto a baking sheet. Bake in the preheated oven for 30-35 minutes, or until the crust is golden brown and beautifully flaky. Once baked, let the galette rest for 5-10 minutes before slicing.