Heat the oven to 400°F (200°C) and line a sheet pan with parchment.
Toss the green beans with the olive oil and half the salt, spread them on the pan, and roast for 8 minutes.
Meanwhile, pat the salmon dry. Mix the melted butter, garlic, lemon zest and herbs.
Push the beans to the edges, place the salmon in the middle, season with the remaining salt and the pepper, and spoon the butter over the fillets. Tuck lemon slices around the pan.
Roast for 10–14 minutes, depending on thickness, until the salmon flakes easily. The USDA recommends 145°F (63°C) internal; many cooks pull it at 125–130°F for a softer texture.
Squeeze the roasted lemon over everything and serve.