Grilled Banh Mi for a Party

Name: Grilled Banh Mi for a Party
Ingredients: Vegetable oil (for grill); 3 medium carrots, peeled, very thinly sliced lengthwise with a vegetable peeler; 1 English hothouse cucumber, thinly sliced into rounds; 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, plus more; 6 red radishes, trimmed, thinly sliced; 1 large jalapeño, thinly sliced; ⅓ cup unseasoned rice vinegar; 1 tsp. plus 1 Tbsp. sugar; 2 lb. ground pork; 1 large shallot, very finely chopped; 6 garlic cloves, finely grated; 2 Tbsp. fish sauce; 2 Tbsp. soy sauce; 1½ tsp. Chinese five-spice powder; 8 kaiser or ciabatta rolls, split; Mayonnaise and cilantro leaves with tender stems (for serving)