Preheat oven to 350°F.
In a large bowl, whisk together the room temperature eggs and heavy cream until smooth. Add the Pecorino Romano, a pinch of salt, and cracked black pepper. Whisk again and set aside.
In a pan over medium heat, add olive oil. Remove the sausage from the casing, crumble it into the pan, and cook until browned and fully cooked through.
Add the minced garlic and cook for another 1–2 minutes until fragrant. Remove from heat.
Add the halved grape tomatoes and chopped spinach into the egg mixture.
Fold in the freshly shredded mozzarella and white cheddar cheese.
Add the cooked sausage mixture directly into the bowl (including the flavorful oils) and mix everything together until combined.
Pour the mixture into a deep dish pie crust.
Bake for 50–60 minutes, or until the center is set.
Let the quiche rest for at least 30 minutes before slicing. Serve warm or cold.