Preheat oven to 400°F.
Cut beets into 1-inch cubes and place on a parchment-lined baking sheet.
Drizzle with avocado oil, orange juice, apple cider vinegar, salt, and pepper. Toss to coat.
Spread evenly and cover tightly with foil. Roast for 30 minutes.
Remove from oven, add water, cover again, and roast 25 to 30 minutes more until tender.
Cool the beets completely.
Whisk together tahini, olive oil, Dijon mustard, lemon juice, maple syrup, and salt.
Add warm water as needed until smooth and creamy.
Toss cooled beets with the dressing.
Mix in sesame seeds, pistachios, and parsley.
Add arugula and toss gently.
Fold in diced avocado just before serving.
Garnish with additional sesame seeds, pistachios, and parsley if desired.
Serve immediately.