Preheat the oven to 425º F.
In a medium bowl, whisk together all the ingredients for the sauce until the cornstarch dissolves.
Place cauliflower and onion on a baking sheet. Drizzle with olive oil, then sprinkle chipotles pepper, salt and pepper, then toss with your hands to combine. Roast for 20 minutes, tossing halfway through.
Drizzle olive oil over peppers in the grill pack. Switch oven to broil and place the grill pack alongside the cauliflower.
Remove the cauliflower and coat with half the stir fry sauce and return back to the oven. Broil both cauliflower and peppers for 3-5 minutes, then remove from oven.
Divide the rice between 4 bowls. Add cauliflower mixture and shishitos to the bowl. Dress with some stir fry sauce, a sprinkle of sesame seed and serve with lime wedges.