Heat your oven to 425ºF and set out a large sheet pan.
Add the chicken to a large bowl and scatter with the garlic powder, smoked paprika, and herbes de Provence and season with salt and pepper. Drizzle with about 2 tablespoons of oil and toss well to coat and evenly distribute the seasoning. Transfer the chicken to the sheet pan, leaving room between each, and roast for 20 minutes.
Meanwhile, in a separate large bowl, whisk 3 to 4 tablespoons of oil with the minced garlic and crushed red pepper flakes. Add in the cherry tomatoes, broccolini, and shallots. Tear the bread into large bite-sized chunks, add to the bowl, and toss well to combine and evenly coat the veg and bread with the oil. Season with salt and pepper.
When the timer goes off, remove the sheet pan from the oven and move the chicken to the centre of the pan. Scatter and arrange the veg and bread around the chicken in an even layer. Nestle in the lemon halves, cut side down, and crumble the feta over the veg. Return the pan to the oven and roast for another 15 to 20 minutes or until the veg is tender and the chicken is cooked through to 165ºF.
Set aside to rest for 5 minutes then serve the chicken and veg scattered with some basil and/or parsley and a little squidge of the roasted lemon juice overtop.