Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
In a large bowl, toss the chopped carrots, parsnips, and red onion with the olive oil, half the sea salt, half the black pepper, and all the dried thyme.
Spread the vegetables in a single layer on the prepared baking sheet and roast for 20-25 minutes until tender and golden brown.
While the vegetables roast, heat a large non-stick skillet over medium-high heat.
Add the lean ground beef to the skillet, breaking it up into small crumbles with a spatula.
Season the beef with the remaining sea salt, black pepper, and the garlic powder.
Cook the beef for 7-9 minutes until fully browned and cooked through, then drain any excess liquid from the pan.
Divide the roasted root vegetables onto plates and top with the savory beef mince to serve.