For the tomato sauce: To a medium saucepan over medium heat, add the olive oil, garlic and red pepper flakes. Cook until the garlic is fragrant, being careful not to burn. Add the cherry tomatoes; toss to combine and coat with the oil. Add the chicken stock and cook until tomatoes burst, about 10 minutes. Hold over medium-low heat.
For the fregola: Bring a medium pot of salted water to a boil. Add the fregola and cook according to package instructions. Drain and toss with the corn. Season with salt.
For the stuffed calamari: Combine rock shrimp, breadcrumbs, parsley and some salt in a food processor. Pulse to a thick paste; add olive oil if needed. Transfer the shrimp paste to a medium pastry bag and pipe into the calamari until three-quarters full. Seal the calamari with skewers.
Simmer the stuffed calamari in the tomato sauce for 5 minutes. Flip and simmer until cooked through, another 5 to 7 minutes.
For the snapper: Heat the oil in a medium saute pan over medium-high heat. Sprinkle the snapper with salt on both sides. Place the fish in the hot pan, skin-side up, for about 3 minutes. Flip and cook on the reverse side for an additional minute or until cooked through. Remove the fish from the pan.
To serve: Spoon the fregola and corn onto a plate, place a snapper fillet and some stuffed calamari on top. Top with tomato sauce.