Fill a large pot with 2 inches of water and bring to a boil over medium heat. Arrange the carrots, asparagus, cauliflower and broccoli in a metal steamer basket; place in the pot and cover. Steam the vegetables until slightly tender but still with a little crunch, 5 to 6 minutes.
While the veggies are steaming, heat a small saute pan over medium heat. Add the sesame-chile oil, olive oil, garlic and pepper flakes, and cook for 1 minute.
Transfer the steamed vegetables to a bowl. Add the sesame-chili oil mixture and the lemon juice, and season to taste with salt and pepper. Toss to coat the vegetables evenly. Serve immediately.