Preheat the oven to 375 degrees.
Cut the leaves off the beets, leaving 1/2" stems, trim the ends.
Put beets on baking tray and drizzle with olive oil, stirring well until roots are well covered.
Cut 1/2" off the top of the garlic bulb and remove any loose outside skins while keeping the bulb whole. Rub with olive oil and wrap in foil.
Put garlic and beets in the oven for 30 minutes, giving beets a stir after 15 minutes. Check that beets are tender with a sharp knife, and check if garlic is ready by squeezing a clove. If it is very soft, remove, if not bake for another 5-10 minutes.
Squeeze the soft garlic cloves out into a bowl and mash with a fork.
Trim the carrots and wash well, peel turnips and cut in half (or quarters, depending on size) and peel rutabagas and cut off tops, cutting each into wedges. Put all onto baking tray with olive oil, mixing well to coat all the vegetables.
Roast for around 25 minutes, turning the vegetables half way through cooking, and then remove from the oven.
Cut the tops and bottoms from the green onions and put in another baking tray with olive oil and bake for 10 minutes, turning half way through cooking.
Peel the cooled beets and cut into quarters.
Now you're ready to prepare the vinaigrette: Put the garlic, red wine vinegar, salt and black pepper into a small bowl and whisk. Slowly add 4-5 tbsp olive, oil whisking all the time, until creamy.
To Serve: Place all the vegetables on a serving platter and drizzle with the vinaigrette. Serve immediately and prepare yourself for effusive compliments which are sure to come!