Roasted Veggie and Black Bean Tacos

medium tomatoes (, cored and seeded, diced* (1 1/2 cups))

ears corn (, kernals cut from cob (1 1/2 cups))

medium zucchini (, diced (1 1/2 heaping cups))

medium yellow squash (, diced (1 1/2 heaping cups))

small yellow onion (, chopped (scant 1 cup))

red bell pepper (, diced (1 cup))

olive oil

canola oil

cumin

chili powder (, divided)

Salt and freshly ground black pepper

canned black beans (, drained, rinsed and warmed)

cilantro (, chopped)

fresh lime juice

Corn or flour tortillas for serving

Queso fresco (, for serving)

Sour cream and Mexican hot sauce for serving ((optional))