1. Preheat the oven to 375 F. Peel the carrots and slice them on a bias (this is prettier than coins and no more work) about 3/4 inch thick.
2. In a large bowl whisk together 1 1/2 tablespoons of the oil, the molasses, cayenne, and a generous pinch of salt and pepper. Add the carrot slices and toss well. Spread the mixture out on a rimmed baking sheet and roast, stirring once or twice, until golden and tender, 25 to 30 minutes.
3. Season the salmon with salt and pepper and rub with the remaining 1/2 tablespoon of olive oil. Place the fish on a small baking pan and pop it in the oven with the carrots during the last 10 minutes. The fish is done when it's opaque on the top but still darker pink inside, 8 to 10 minutes depending on how thick the fillets are. You should be able to cut into it with a fork, but it shouldn't flake (that's overdone).
4. Serve the salmon and carrots garnished with herbs, if you have them, and lemon wedges.