The best time for transplanting any shrub is when it is dormant (in or near winter, before the ground freezes) so transplant shock is somewhat reduced. Some people prefer to transplant in winter closer to the time when the plant is going to leaf out but you cannot go wrong either way. You can also transplant in early spring (my choice), after the plant has leafed out, provided you wait at least two weeks after your average date of last frost. This is preferable from the standpoint that the ground may be workable in early spring (as opposed to the ground/weather being frozen/cold/miserable during winter).
I would water well the day before moving, and prepare the hole before digging out the rose. The hole should be deeper and wider than the rootball so be ready to tweak the new hole when transplanting if it is not as deep or wide. You can add some compost and organic fertilizers/amendments like bone meal, cottonseed meal and-or bone meal. The A. R. S. suggests a hole size of 2 by 2 by 2 feet (or 0.6 x 0.6 x 0.6 meters) for a new shrub. I can't dig a rootball that size so I try to move as much as I can.
Place the shrub above the amended soil and start adding soil around the rootball. Make sure the shrub is at the same height relative to the surrounding soil as before. If it is not, adjust it. Now is the time for that. Press on the new soil lightly to get rid of air pockets. Add more soil if needed. Cover with 3-4" of mulch.
Note: I like to add bone meal all around the bottom of the rootball. Water when done and water regularly; more often than usual at first. Do not add fertilizers like blood meal or cottonseed meal if planting in winter but bone meal is ok.