Adjust oven racks to top and middle positions and preheat to 450°F.
Toss potatoes and carrots with 2 teaspoons olive oil and 1 teaspoon thyme. Sprinkle with salt and pepper. Roast on the top rack until browned and tender, 20 - 25 minutes.
While the potatoes and carrots are roasting, melt the butter in a small saucepan, and let cool slightly. Stir in the almonds, bread crumbs, and remaining thyme. Add a pinch of salt and pepper.
In a small bowl, combine the maple syrup and mustard.
Pat the trout dry with paper towels and season with salt and pepper. Drizzle skin sides with oil and rub to coat. Once the potatoes and carrots have cooked for 12 minutes, place trout skin sides down on a second baking sheet. Spread a thin layer of maple mustard sauce (reserve remaining sauce for serving). Mound with almond mixture, pressing firmly to adhere.
Transfer potatoes and carrots to middle rack and place trout on the top rack. Roast until crust is golden brown and trout is cooked through, 10 - 12 minutes.
Divide trout, potatoes, and carrots between plates. Drizzle trout with remaining maple mustard sauce and serve.