Rest steak on a cutting board so the grain of the beef is running horizontally. Season liberally with salt and pepper, then flip the steak.
2.5 lbs flank steak, 2 teaspoon fresh cracked pepper, 3 teaspoons coarse kosher salt
Add roasted red peppers, crushed red pepper, olive oil, garlic, coriander, cumin, and sea salt to a food processor. Blend to combine until creamy and smooth.
1 teaspoon crushed red pepper, 2 Tablespoons olive oil, 1 teaspoon ground coriander seeds, 1 teaspoon ground cumin, 1 teaspoon sea salt, 4 cloves garlic, 4 roasted red peppers
Spread the blended harissa sauce evenly over the beef. Leave 1-inch along the top side of the meat uncoated. Top the sauce with roasted garlic and parsley.
8 cloves roasted garlic, 3 Tablespoons parsley
Tightly roll the steak from top to bottom so the grain of the beef runs along the length when rolled. Tie with butcher's twine with two inches of space between each tie. Wrap with plastic wrap and refrigerate for at least 4 hours, up to overnight (for best results).
Preheat half your grill to medium-high heat (375°F-450°F). Sear the beef roulade over direct heat, rolling so it forms an even sear, for 5-10 minutes. Once seared, move the roulade to indirect heat to finish cooking. The internal temperature should reach 130°F - use a meat thermometer to check the internal temperature. Allow it to rest for 10 minutes before removing the twine and slicing into half-inch slices.