Roast: Preheat the oven to 450°F. Combine the oil, salt and garlic on a baking sheet. Add the mushroom, zucchini, and corn. Mix well and bake until tender and roasted, about 20 minutes, stirring midway through cooking time. If you have more time, roast until the corn is golden, an additional 5 to 10 minutes. Keep warm.
Quinoa: Heat the broth, salt, quinoa and garlic in a large pot. Cover, bring to boil over high heat, reduce to medium-low heat and cook for 15 minutes. Remove from heat and set aside for 10 minutes to steam. Fluff with fork and set aside.
Pasta: Heat the oil in a medium saucepan over medium-high heat. Add the orzo and cook, stirring frequently, until golden brown. Add the water and salt and bring to boil. Reduce to simmer and cook until tender, 7 to 9 minutes. Drain and set aside.
Greens: Add the orzo to the cooked quinoa. Add the roasted vegetables to the quinoa. Add the arugula, scallions, serrano and lemon juice. Stir well, taste and adjust seasoning with salt and black pepper.