Put the wild rice in a saucepan and cover with plenty of salted water. Bring to a boil, then reduce the heat to a gentle simmer and cook the rice until it is tender, about 45 minutes.
While the rice is cooking, preheat the oven to 375ºF (190ºC). Drizzle a few spoonfuls of olive oil on a rimmed baking sheet, spread the cubed root vegetables over the pan, and season well with sea salt and freshly ground black pepper.
Toss the vegetables with the olive oil to coat and spread them in an even layer on the baking sheet. Bake for 30 to 45 minutes, stirring once or twice during cooking, until the vegetables are fully cooked and caramelized.
When the rice is done, drain it well and toss it in a large bowl with the cooked vegetables. Let the mixture cool to room temperature, then stir in the minced spring onions and chopped herbs.
Make the lemon-tahini dressing by stirring together the tahini, fresh squeezed lemon juice, water, minced garlic, and soy sauce. Pour the dressing over the salad and stir it in well, then taste and add a bit more salt or lemon juice if desired.