Heat oven to 400°F. In a bowl, combine tomatoes, zucchini, 1/2 onion, garlic, jalapeno, 1/4 teaspoon salt and oil; toss to coat. Spread on a baking sheet coated with cooking spray; roast, turning once, until tomatoes and zucchini are light brown, 20 to 25 minutes. Toss with 1/4 cup cilantro and 1 tablespoon juice; set aside. In a second bowl, combine flour, cumin, baking powder and remaining 1/4 teaspoon salt. Add egg, remaining 1 tablespoon juice and 1/2 cup water; stir until smooth. Add corn and remaining 1/2 onion and 1/4 cup cilantro. Coat a large frying pan with cooking spray and heat over medium-high heat. Form 1/4 cup corn mixture into a patty; repeat with remaining corn mixture to form 12 patties. Working in batches of 3 and coating pan with cooking spray as needed, cook patties, turning once, until brown, 5 to 8 minutes per side. Divide patties and salsa among 4 plates.