01 - Preheat a grill to medium-high heat, approximately 375 to 400 degrees Fahrenheit.
02 - Brush the halved tomatoes, onion slices, and bell pepper with 1 tablespoon of olive oil, coating evenly on all sides.
03 - Place the sausages and oiled vegetables on the grill. Cook sausages for 10 to 12 minutes, turning occasionally, until evenly charred and cooked through to an internal temperature of 160 degrees Fahrenheit. Grill vegetables for 4 to 6 minutes until softened and lightly charred, then remove from the grill.
04 - Allow the grilled vegetables to cool slightly, then coarsely chop them into bite-sized pieces and set aside.
05 - In a skillet over medium heat, warm the remaining 1 tablespoon of olive oil. Add the minced garlic and sauté for 1 minute until fragrant. Add the chopped grilled vegetables and season with salt, pepper, dried oregano, and crushed red pepper flakes. Cook for 3 to 4 minutes, stirring often, until the flavors meld together. Remove from heat and stir in the fresh basil and parsley.
06 - Split each grinder roll lengthwise without cutting all the way through. Place the rolls cut-side down on the grill and toast for 1 to 2 minutes until lightly crisp and golden.
07 - Place one grilled sausage into each toasted roll. Spoon the grilled tomato sauce generously over each sausage. Top with shredded mozzarella or provolone cheese if desired.
08 - Return the assembled grinders to the grill over indirect heat, cover, and cook for 1 to 2 minutes until the cheese is melted. Serve immediately, garnished with extra fresh basil if desired.