Preheat oven to 425°F and line baking sheet with parchment paper.
In a medium bowl, toss the red onion, bell peppers, vinegar, ¼ teaspoon salt, and ½ teaspoon oil. Spread evenly over the prepared baking sheet.
Place in the oven and roast for 15-20 minutes, until caramelized. While the red onion and bell peppers roast, heat the remaining ½ teaspoon of oil in a large nonstick skillet over medium-high heat.
Add the diced onion and the garlic. Sauté until lightly browned, about 3 minutes.
Add cumin, fennel, and cinnamon. Sauté for 1 more minute.
Add ¼ teaspoon salt, ¼ cup water, olives, raisins, black pepper, tomatoes, chickpeas, and potatoes; bring to a boil.
Cover, reduce heat, and simmer the chickpea tagine for 25 minutes or until potatoes are just tender.
Add additional water as necessary to just cover the ingredients as they simmer.
Serve the roasted vegetables and tagine over a bed of whole wheat couscous. Enjoy!