Cook tortellini as directed on package. Drain and rinse; set aside.
In a large deep skillet, or a dutch oven, heat olive oil over medium heat. Mince garlic and add to hot oil; saute for 30 seconds. While whisking, add in flour and onion powder.
Continue to whisk, cooking for 1 minute, then add milk. Cook until sauce becomes bubbly and thickened, stirring frequently.
Add drained tomatoes, roughly chopped spinach, fresh chopped basil, oregano, salt, and pepper. Cook until spinach has wilted.
Stir in grated Parmesan and tortellini. Cook 4-5 minutes to heat through.