Congrats. I'm currently in my fourth year regrowing geraniums I stored bare-root in the basement. I just remove most of the dirt from the roots and put the plants upside down in boxes on the floor in a dark basement room. The temperature down there stays above 60, which sounds high, but the plants do very well.

The first couple winters I soaked the roots a couple times, but I've found that doesn't help their survival. What I have found is that first-year plants with thinner stems just need to be restarted a little early the following spring. Once a geranium is two or more years old it will have thicker stems and will easily survive the winter. My third and fourth-year plants are so mature and thick I could leave them bare-root in the boxes through summer and they'd still be fine. Once I cut them back and pot them up in spring they begin to put out growth in about five days, and then they grow very quickly. I used to pot them up in March, but because of their high growth rate I now wait until sometime in April.