Preheat the oven to 400°F (200°C).
In a small bowl, mix together 2 tablespoons of olive oil, minced garlic, oregano, thyme, salt, and black pepper.
Place the salmon fillets on a baking sheet lined with parchment paper. Brush the garlic herb mixture over the top of each fillet. Place lemon slices on top of the salmon.
In a large bowl, toss the broccoli, baby carrots, and bell peppers with the remaining 2 tablespoons of olive oil, salt, and pepper until evenly coated.
Arrange the vegetables around the salmon on the baking sheet.
Roast in the preheated oven for 15-20 minutes, or until the salmon flakes easily with a fork and the vegetables are tender.
Remove from the oven and let it rest for a few minutes before serving.