Preheat the oven to 400 F. Toss the cauliflower, carrot, onion, and chipotle pepper on a sheet pan, salt to taste. Roast for about 10 minutes, until browned in spots. Keep warm.
In a blender or food processor, combine the parsley, cilantro, garlic, half the pepitas, and process to mince. If necessary, scrape down and repeat. Add the vinegar, olive oil, shallot, oregano and salt and process to make a chunky paste. Scrape into a small bowl.
For each bowl, spread a cup of cooked rice in a wide bowl, and arrange 1/4 of the cauliflower, peppers, olives, avocado and some chopped shallot on top. Drizzle with chimichurri to taste and sprinkle with the remaining toasted pepitas. Serve.