Preheat the oven to 180°C.
Dice the vegetables, mix with 2 tbsp olive oil, season with salt and pepper and sauté in a skillet for 8-10 minutes until tender and golden-brown. Set aside.
Rinse fish fillets, pat dry with a kitchen towel, season with salt and pepper and sauté in a heated skillet over high heat with 1 tbsp olive oil, skin-side down for 2-3 minutes, until the skin is crispy and golden.
Arrange roasted vegetables and fish fillets skin-side up in a baking pan, drizzle with olive oil, chop fresh thyme and sprinkle on top.
Bake for 10-15 minutes until the fish is cooked through - the flesh should be white and flaky.