Preheat oven to 450 degrees. Place tomatoes and thyme in a 9" pie plate. Drizzle with olive oil, season with salt and pepper, and toss to coat. Bake for 20 minutes, stirring halfway through. Remove from the oven and let cool. Reduce oven temperature to 400 degrees.
Make the onion frittata:
In a large bowl, whisk together eggs and next seven ingredients (Pecorino Romano cheese through pepper). Set aside.
Heat olive oil in a 9" oven-safe fry pan over medium-high heat. Add onion and cook until lightly caramelized, about 8 minutes.
Reduce heat to low, add egg mixture to fry pan and spoon dollops of ricotta on top. Cook, without stirring, for 2 minutes.
Bake for 7-9 minutes until slightly puffed and golden.
Remove from the oven and garnish with roasted tomatoes. Cut into wedges and serve warm.
Recipe by Two of a Kind at http://www.twoofakindcooks.com/onion-frittata-roasted-tomatoes/