Preheat oven to 400°F (200°C). Line two large baking sheets with parchment paper.
Toss vegetables (broccoli, Brussels sprouts, sweet potato) with 2 tablespoons olive oil, half the garlic powder, paprika, salt, and pepper on one baking sheet. Spread in single layer with space between pieces.
Prepare chickpeas by tossing dried chickpeas with remaining olive oil and seasonings on second baking sheet.
Roast vegetables for 20-25 minutes, turning halfway through, until tender with browned edges.
Roast chickpeas for 15-18 minutes until crispy and golden, shaking pan once during cooking.
Make tahini dressing by whisking together tahini, lemon juice, maple syrup, and Dijon mustard. Add water gradually until pourable consistency is reached. Season with salt and pepper.
Assemble bowls by dividing roasted vegetables and crispy chickpeas between serving bowls. Drizzle generously with tahini dressing and garnish with fresh herbs.