Change-up this sheet pan dinner by trying another flavor variety of bratwurst such as beer brats, bacon and cheese, or pineapple. If fingerling potatoes aren't available, swap in baby red or gold potatoes.
Preheat oven to 425°F. Line 2 large baking pans with foil. In a large bowl toss cabbage in oil. Place wedges, cut sides down, on one of the prepared pans (allow excess oil to drip back into bowl). Toss potatoes in remaining oil in bowl. Place potatoes, cut sides, down on the other prepared baking pan (allow excess oil to drip back into bowl and reserve bowl). Nestle 3 garlic cloves and 2 sage sprigs in each pan and sprinkle with salt and pepper. Cover pans tightly with foil; roast 20 minutes.
Remove foil covers from pans. Lightly prick the bratwurst and toss in remaining oil in bowl; add to pan with cabbage. Switch pans to opposite oven racks and continue roasting 15 minutes. Turn cabbage, potatoes and bratwurst; continue roasting about 5 minutes more or until tender, golden, and cooked through (bratwurst should register 160°F). Transfer cabbage, potatoes, and bratwurst to a large platter.
In a small skillet melt butter over medium just until foam subsides. Add sage leaves. Cook 30 to 60 seconds or until butter is brown and nutty and sage is crisp; spoon mixture over cabbage, potatoes, and bratwurst on platter.