Preheat the oven to 400 degrees F (200 degrees C).
Mix potatoes, 1 teaspoon olive oil, 1/4 teaspoon black pepper, rosemary, and sea salt together in a bowl. Place on a baking sheet.
Bake in the preheated oven until golden brown and tender, stirring once, about 35 minutes.
Reduce oven heat to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan with cooking spray.
Heat remaining 1 teaspoon olive oil in a skillet over medium-high heat. Saute onion until translucent, about 3 minutes. Add kale and tomatoes; cook until wilted, about 2 minutes. Remove from heat.
Pour onion mixture into a bowl. Add the roasted potatoes, eggs, Greek yogurt, milk, water, feta cheese, Parmesan cheese, and 1/2 teaspoon salt; whisk until combined, adding more water if needed. Pour into the prepared baking pan.
Bake in the preheated oven until center is solid, about 25 minutes.
