Preheat your oven to 400°F (200°C). Line a large baking sheet or roasting pan with parchment paper or lightly grease it with olive oil.
In a small bowl, mix together the olive oil, minced garlic, chopped rosemary, salt, and pepper. Rub the mixture all over the chicken thighs, making sure to get it under the skin for maximum flavor.
Place the seasoned chicken thighs on one side of the prepared baking sheet.
In a large bowl, toss the baby potatoes, carrots, red onion, and bell pepper with olive oil, salt, and pepper. Spread the vegetables in a single layer on the other side of the baking sheet alongside the chicken.
Place the lemon slices over the chicken thighs and scatter a few among the vegetables for extra flavor as they roast.
Roast in the preheated oven for 35-45 minutes, or until the chicken is golden brown, crispy, and cooked through (internal temperature of 165°F or 75°C) and the vegetables are tender.
Halfway through roasting, toss the vegetables to ensure even cooking and crispness.
Remove the chicken and vegetables from the oven and let them rest for 5 minutes. Serve the Roasted Rosemary Chicken and Vegetables with a squeeze of fresh lemon juice for a bright finish.
