Preheat your oven to 375F. Toss all of the tomatoes and the chickpeas (it's fine to mix them all together) in the olive oil and a generous sprinkle of salt and black pepper.
Transfer the tomatoes and the chickpeas to one or two parchment-lined baking sheets (big enough to hold them all in a single layer). Break the head of garlic into cloves. Without peeling the cloves, nestle them in between the tomatoes and chickpeas on the baking sheets. Use all of the cloves. Roast the tomatoes and chickpeas for 15-25 minutes, or until the tomatoes are browning and collapsing and the chickpeas are crispy. Check them once, halfway through, gently nudging them around if they're sticking to the parchment.
While the tomatoes and chickpeas roast, rinse the quinoa through a fine sieve for about a minute. Drain the quinoa and then place it in a medium sized saucepan with 2 cups of water. Bring the quinoa to a boil and reduce it to a simmer. Cover the quinoa and simmer for 15 minutes, or until all of the water has been absorbed. Turn off the heat and fluff the quinoa with a fork. Cover it again and allow it to rest for ten minutes.
Remove the garlic cloves from the roasted tomatoes and chickpeas. If the cloves are on the bigger side, then you can squeeze them into the dish for extra garlicky flavor, or you can save them and squeeze the roasted interior of the cloves into polenta, pasta, or hummus. Smaller cloves will probably dry up in the cooking process, in which case you can just discard them.
In a large mixing bowl, combine the cooked quinoa with the tomatoes, chickpeas, balsamic vinegar, and chives. Mix it all well, and then season to taste with additional salt and pepper and an extra drizzle of olive oil, as well as any additional dried or fresh herbs you like (oregano and thyme would be lovely). Serve.
Leftover quinoa will keep for up to three days in an airtight container in the fridge.