Spicy Seattle Tuna Rolls

1 tablespoon plus 1 teaspoon grated peeled fresh ginger

1 tablespoon toasted sesame seeds

1 garlic clove, coarsely chopped

1/2 teaspoon kosher salt plus more for seasoning

1/4 cup sunflower or vegetable oil

2 teaspoons toasted sesame oil

1 teaspoon distilled white vinegar

1 pound sashimi-grade yellowfin tuna fillets, cut into 1/8" cubes

4 toasted dried nori sheets, halved lengthwise

1 1/2 cups (about) cooked short-grain rice, cooled

Assorted fillings, such as sliced scallions, English hothouse or Persian cucumbers, cilantro leaves, and chive blossoms

Ingredient info: Look for Thai chiles, nori, and chive blossoms at better supermarkets and at Asian markets.