Place quinoa, salt, and water in a small saucepan.
Bring to a boil over medium-high heat.
Lower heat to a simmer, cover, and cook for 15 minutes.
Remove from heat and let sit for 5 minutes.
Uncover and fluff with a fork.
Preheat oven to 425°F.
Arrange chopped vegetables on a baking sheet.
Drizzle with avocado oil, salt, pepper, garlic powder, and thyme.
Toss the vegetables and spread into an even layer.
Roast until fork-tender, about 30 minutes.
Flip vegetables and broil on high for 5 minutes.
Divide quinoa among four bowls.
Top with roasted vegetables and chopped cilantro.
Drizzle with tzatziki sauce and serve immediately.