Root Vegetable Tacos with Pineapple Salsa

garlic (unpeeled)

large red onion, cut into thin wedges

medium sweet potatoes, cut into 1-inch chunks

medium celery root, trimmed, peeled and cut into 1-inch chunks

vegetable oil

Kosher salt and freshly ground pepper

pineapple, cored

serrano chile pepper

fresh cilantro, chopped

fresh lime juice

vegetarian refried beans

6-inch corn tortillas