In a small bowl, combine the chopped parsley, minced garlic, dried oregano, red pepper flakes, salt, and black pepper.

Stir the red wine vinegar into the herb mixture, then slowly whisk in the olive oil until well combined. Set the chimichurri aside to let the flavors meld.

Preheat your grill or a heavy grill pan over medium-high heat. Place the chorizo sausages on the grill and cook for about 12 to 15 minutes, turning occasionally, until nicely browned and cooked through.

During the last 2 minutes of cooking, slice the crusty rolls in half horizontally and place them cut-side down on the grill to toast until light golden brown.

To assemble, butterfly the cooked sausages by slicing them lengthwise without cutting all the way through, and open them flat. Place one butterflied sausage on each toasted roll, generously spoon the chimichurri sauce over the meat, and serve immediately.