Are they still dormant? If so it should be fine to plant now. If they are starting to bud or have leaves then wait until after last frost. The frost would be one heck of a shock. Keep moist/wet in a bucket if bareroot
I would also recommend acclimatizing if they have been kept indoors more than a day or two. Set them in a cold room, enclosed porch, etc for a few days before giving the full monty of old man winter.