Preheat Oven: Preheat the oven to 425°F. Line a rimmed baking sheet with parchment paper.
Cut Tomatoes: Slice the grape tomatoes in half lengthwise and place them in a large mixing bowl.
Season Tomatoes: Add the olive oil, garlic powder, dried oregano, and salt. Toss gently until the tomatoes are evenly coated.
Arrange Tomatoes: Spread the seasoned tomatoes cut-side up in a single layer on the prepared baking sheet.
Roast Tomatoes: Roast the tomatoes for 14 to 16 minutes, until softened, lightly browned, and beginning to release their juices.
Reduce Balsamic: While the tomatoes roast, pour the balsamic vinegar into a small saucepan. Bring it to a gentle simmer over medium heat, then reduce the heat to medium-low and cook for 8 to 10 minutes, stirring occasionally, until slightly thickened and reduced by about half. Remove it from the heat and let it cool.
Cool Tomatoes: Remove the tomatoes from the oven and let them cool for about 5 minutes. This keeps the hot filling from weakening the rice paper wrappers.
Prepare Mozzarella: Tear the fresh mozzarella into small, bite-size pieces. Divide the mozzarella, roasted tomatoes, basil, and romaine into eight equal portions.
Soften Rice Paper: Fill a shallow bowl with warm water. Dip one rice paper wrapper into the water for about 5 seconds, or until it begins to soften. Place it flat on a clean work surface and allow it to soften for a few more seconds.
Layer Fillings: Place one basil leaf near the lower third of the wrapper. Top it with one portion each of shredded romaine, mozzarella, and roasted tomatoes, keeping the filling in a compact row.
Fold Wrapper: Fold the lower edge of the rice paper over the filling. Fold both sides inward to help contain the ingredients.
Roll Summer Roll: Continue rolling the wrapper tightly but gently until the filling is fully enclosed. Repeat with the remaining wrappers and fillings.
Serve Rolls: Serve the summer rolls immediately with the cooled balsamic reduction on the side for dipping.