How big around are they and how many shoots can you see on the rhizomes? If they only have one shoot, it grows and then freezes and dies, you're probably SOL unless it has been going for a while or is a nice fat rhizome.
If there is more than one bud per rhizome, it should be fine even if it freezes unless it is a crazy hard freeze and all of them have grown above the soil.
I would check the weather for the next week or so. If you're not expecting a hard freeze, plant them. Then keep an eye on the weather - once they sprout above the soil, if you are worried about a freeze just cover them with an upturned pot overnight, they should be fine.
Btw, I just checked MN weather - there is a freeze alert for a good chunk of the state, so I would wait until Wednesday or Thursday and then plant them.