Place the tomatoes on a rimmed baking sheet and liberally drizzle with oil. Sprinkle with salt and pepper then toss. Roast until softened and bubbly, rotating the sheet and gently shaking the tomatoes around halfway through, about 20 minutes total.
While the tomatoes roast, bring a medium saucepan of water to a boil and season with salt. Add the orzo and cook according to the package directions until al dente, stirring occasionally. A minute before the pasta is done, add the broccoli and cook for 1 minute. Drain.
Pour the roasted tomatoes along with any juices into a large bowl. Add the vinegar and toss together. Add the pasta and broccoli along with the chicken, scallions and parsley. Toss and season with salt and pepper. Taste for seasoning and drizzle with olive oil if desired.
Serve warm or at room temperature. Or refrigerate for up to 5 days and serve cold.
If you can't find baby tomatoes, use any combination of cherry, grape or pear tomatoes in assorted colors.