Transplanting Rivermallow Bushes?

I have two Rivermallow bushes that have been growing in my garden for four years. They have gotten huge and I desperately need to dig them up and move them. I was told to do this in the fall, but the bushes have a huge root system. I was wondering if it is safe to dig them up because I am obviously going to do some damage to the roots. Will they be alright if I do this?

Hardiness Zone: 5b

By Lisa Damiano from Chambersburg, PA