Add all of the parsley, cilantro, jalapeños, garlic, and vinegar to a blender. Purée until smooth. With the motor running, drizzle in the oil until emulsified. Season to taste
Coat the tofu in half of the chimichurri sauce and marinate for 4-12 hours.
Preheat the oven to 425°F.
On one or two baking sheets, toss the root vegetables with the oil, salt and pepper. Roast for 15-20 minutes, or until softened and starting to caramelize on the edges. Remove from the oven and toss with the scallions.
Heat a large grill or griddle over high heat. Brush the marinated tofu and red onions with oil and when the grill is very hot, sear the tofu and onions for 3-4 minutes per side, until charred.
Divide the roasted root vegetables, tofu and onions between plates. Drizzle with reserved chimichurri sauce.