Are the canes still green? If so keep them in the sun and watered and they should eventually leaf out. If the canes are brown or withered looking prune them back to good healthy green cane with a white/creamy center. Even if that's to the soil line. Most minis are own root and they may come back from the roots but that will take a little more time.

I would recommend in the future that you water them over the winter at least once a month. Dehydration is one of the quickest ways to kill a dormant rose. Think of them as sleeping, not dead, and water them.

Thanks. Nothing looks green or healthy--all pretty much like dried twigs. I'll cut back little by little to see if I can find any healthy white centers. Obviously, I'm new to this. Ordered 5 more minis and have them in pots; don't want this to happen next year.

"Dried twigs" says "dead" to me. You can dig down beneath the soil surface to see if there is any green down below. If no sign of green, then punt. As seil said, even when overwintered in a garage the soil needs to be kept moist.