Preheat oven to 400 degrees. Line a rimmed 18 by 13-inch baking sheet with parchment. Place squash on baking sheet on upper third portion of baking sheet then place broccoli in the middle portion and red onion on bottom portion*. Drizzle veggies with 4 tsp olive oil, season with salt and pepper and toss while keeping veggies separated in each section. Roast in preheated oven 8 minutes. Meanwhile in small bowl stir together mustard, honey, 1 tsp of the olive oil, 1 minced clove garlic and lemon juice, set aside.