Prep: Adjust rack to middle position ans preheat oven to 450 degrees. Wash and dry all produce. Mince garlic. Trim and discard woody bottom ends from asparagus; but stalks crosswise into 3-inch pieces. Strip thyme leaves from stems; discard stems and roughly chop leaves. In a small pot, combine stock concentrate and 2 cup water. Bring to a simmer over medium heat.
Roast Veggies: Toss garlic, asparagus, tomatoes, and half the thyme on a baking sheet with a drizzle of olive oil, salt, and pepper. Roast, tossing halfway through, until asparagus is tender and tomatoes burst, 12-15 minutes.
Cook Scallion whites: Meanwhile, trim and thinly slice scallions, separating whites from green. Melt 2 TBSP butter in a medium pot over medium heat. Add scallion whites and cook, stirring, until fragrant, 1 minute.
Toast Couscous: Add couscouse and remaining thyme to same pot. Cook, stirring, until grains are lightly toasted, 1-2 minutes.
Simmer Couscous: Pour simmering stock into pot with couscous mixture. Reduce to a low simmer, cover, and cook until tender, 6-8 minutes. Drain any excess liquid from pot, if necessary.
Serve: Fluff couscous with a fork; season with salt and pepper. Divide between plates, then top with roasted veggies. Sprinkle with almond, feta, and scallion greens.