Unroll crescent rolls and form a large rectangle by pinching seams together. Cut the dough to form 12 small rectangles.
Cut each piece of string cheese into 4 sections.
On each dough rectangle, sprinkle a pinch of cheddar cheese and top with a string cheese section. Fold dough over the cheese so the dough forms a ball over the cheese. Pinch seams together.
Pour enough vegetable oil into a small saucepan, electric skillet, etc until it is 4 inches deep. Heat the oil until it reaches 350°. Carefully drop the cheese bombs into the hot oil. Scoop out with a mesh wire spoon and lay on a paper towel covered plate. Dust with parmesan cheese.