Step 1 Preheat oven to 200°C. Line a baking tray with baking paper. Wrap each beetroot tightly in foil and place on prepared baking tray; roast for 40–45 minutes.
Step 2 Toss Brussels sprouts in half of the olive oil; add to beetroot tray.Cook for another 20–25 minutes, or until beetroot is tender when tested with a knife and sprouts are golden brown.
Step 3 Meanwhile, bring vegetable stock to the boil in a medium saucepan set over high heat. Remove pan from heat, cover to keep warm and set aside.
Step 4 Heat remaining olive oil in a large heavy-based saucepan set over medium heat. Add onion and garlic; cook gently, stirring occasionally, for 5 minutes, or until transparent. Add arborio rice; stir to coat grains with oil. Increase heat to medium–high.
Step 5 Add wine and thyme sprigs; cook for 2–3 minutes, or until wine is bubbling. Add reserved stock one-third at a time, stirring occasionally and allowing rice to absorb stock between additions. (This absorption process takes about 15–20 minutes. If you run out of stock and rice needs more cooking, add a little hot water.)
Step 6 Meanwhile, rub off beetroot skin and discard. Dice beetroot; set aside. Once rice is al dente, stir in beetroot and add half of the roast Brussels sprouts.
Step 7 Top risotto with remaining sprouts and feta; scatter with parsley (or dill) and serve.