In the kitchen, salmon is as versatile as a fish could ever hope to be. It's rich enough and moist enough to stand up to any cooking method, even the dry heat of your oven. Your only real risk is overcooking it, which can dry out and toughen the salmon's delicate flesh. You can avoid that by paying careful attention to your roasting time or by cooking at a lower temperature.
One common method of roasting salmon calls for high-temperature cooking. This has the advantage of quick cooking time, and the high temperatures give your salmon pieces an attractively browned surface. They'll also caramelize any sauce or glaze you choose to use, providing deeper flavors. You can cook boneless fillets or salmon steaks at 425 to 450 degrees Fahrenheit, allowing approximately 8 minutes per inch of thickness. For whole salmon, turn the heat down to 400 F and allow 10 minutes per inch of thickness at the thickest point.
Salmon is naturally high in unsaturated fats, which is why it won't dry out in high-temperature roasting. However, like red meats, it can also benefit from longer cooking at lower temperature. This gives the flesh time to cook gently and evenly, avoiding the risk of your portions being overcooked at the edges but undercooked in the center. Use a temperature of 325 F for fillet portions, or as low as 275 for whole fish, and cook for up to 15 minutes per inch of thickness. If you want crisply browned skin or a caramelized sauce, finish the salmon under your broiler for a minute or two.
High-temperature roasting makes for a quick meal, but at some risk of overcooking the salmon. Slow baking takes longer, but requires less of your attention and minimizes the risk of dry, overcooked fish. A third technique -- cooking your salmon in a pouch of parchment paper, or "en papillote" -- gives you the best of both worlds. Place each portion of salmon on a square or round of parchment, and lift up the edges. Fold the edges together to seal the pouch, then bake the salmon at your normal roasting temperature. The parchment traps its moisture, helping keep the portion juicy even if you've overcooked it slightly.
A Few Tips
Regardless which technique you choose, a few tips will help you get a better result. First, get a meat thermometer or instant-read thermometer. Your salmon is ready once its internal temperature reaches 145 F. Thick pieces can come out at 140 F, because they'll continue cooking to 145 F after they're out of the oven. For more even cooking, fold the thin belly section of your fillets underneath the rest of the portion. That makes it thicker, and less prone to overcooking. If you're working with a whole fillet, you can also fold the thinner tail portion underneath or shield it with aluminum foil.