Preheat oven to 400°F. Place tortillas in a single layer on two baking sheets. Coat each tortilla with nonstick cooking spray on one side, flip and coat on the opposite side. Bake for 8-10 minutes, flipping halfway through cooking time, until golden brown. Transfer to a wire rack to cool completely.

On a baking sheet toss vegetables and asparagus with oil, 1/2 teaspoon kosher salt, pepper, cumin and chili powder. Roast for 15-20 minutes, or until vegetables begin to brown at the edges.

To assemble tostadas, line a baking sheet with aluminum foil. Spread each tortilla with a layer of refried beans. Top with shredded cheese and roasted vegetables. Place tostadas on a baking sheet and cook for 5 minutes, or until cheese is melted.

While tostadas bake, make lime crema by whisking together sour cream, lime juice, and remaining 1/2 teaspoon kosher salt. Top tostadas with lime crema, salsa, sliced avocado and garnish with cilantro.