Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
In a large bowl, toss the green beans with the olive oil, ¼ teaspoon of salt, and ¼ teaspoon of pepper. Spread on the baking sheet, leaving space in the center of the baking sheet. Place the salmon in the center of the baking sheet.
In a small prep bowl, combine the paprika, garlic powder, oregano, cayenne, and remaining ¼ teaspoon of salt and ¼ teaspoon of pepper. Spread on top of the salmon.
Place the baking sheet in the oven, and bake for about 15 minutes, or until the salmon flakes easily with a fork and the green beans are tender.
Meanwhile, prepare the watermelon salsa. Combine the watermelon, red onion, cilantro, jalapeno, lime, olive oil, and salt in a bowl. Stir well.
When the salmon and green beans are done cooking, divide into four portions and top the salmon with the watermelon salsa.