Roasted Purple Cauliflower and Arugula Salad

Name: Roasted Purple Cauliflower and Arugula Salad
Ingredients: For the salad; 1 medium head purple cauliflower, broken into florets; 1 tablespoon olive oil; several shakes of salt and black pepper; 6-7 ounces fresh arugula; For the vinaigrette:; 2 tablespoons olive oil; 1 1/2 tablespoons sherry vinegar; 2 teaspoons grainy/spicy mustard; 1 teaspoon lemon zest (about half of 1 lemon); 1 teaspoon lemon juice; 2 teaspoons finely chopped fresh rosemary; 1/2 teaspoon salt; 1/4 teaspoon black pepper