Slice 3-4 beets into 1/4″ thick rounds, then cut into small dice.
Shuck 2 ears of corn and cut the kernels off the cobs.
Trim green beans and dice to make 2 C.
Saute the onion in 3 T. olive oil until tender. Toss in a bowl with the other vegetables along with 1 t. cumin and 1 t. coriander power plus salt and pepper.
Place the veggies on a cookie sheet or sheets in a single layer. Roast until everything is tender and beginning to caramelize.
In a small bowl, mix 1 C. plain yogurt with 1 t. of “adobo sauce” from a can of Chipotle peppers. Season to taste with salt, and add more chipotle if you like.
Serve the roasted veggies in warm flour tortillas. Top with the salsa and the chipotle sauce. You can also add grated cheese, cooked beans, or other fillings.