Preheat a grill to medium-high (400°F to 450°F). Melt butter in a small skillet over low; add garlic. Let garlic simmer in butter over low while sausages grill.
Place sausages on oiled grates; grill, uncovered, turning often, until sausages are thoroughly cooked with a crisp casing. Remove sausages from heat. Brush inside and outside of sub rolls with garlic butter; place on grill until golden and toasted, about 1 minute.
Mix up your hot-dog repertoire by adding a different type of sausage.