Preheat oven to 220 degrees. Coat a baking sheet with olive oil spray.
Toss squash and bell pepper with two teaspoons of the oil, thyme, 1/4 teaspoon salt and 1/8 teaspoon freshly ground black pepper in medium bowl.
Arrange in single layer on prepared baking sheet. Roast 25 to 30 minutes, stirring occasionally, until tender and lightly browned. Let cool 10 minutes.
Whisk lemon juice, honey, remaining oil, 1/4 teaspoon salt and 1/8 teaspoon black pepper in large bowl.
Add onion, spinach, apple, cabbage, sunflower seeds and squash mixture. Toss to combine.