Answer: With an established plant the roots generally extend well beyond the branch spread, sometimes twice as far. Your plants are relatively newly planted so I would not expect the roots to have spread terribly far yet, but I would not plan on them being only as wide as the branches. Begin well outside the original root area and check for roots, also dig deep below the plant to take as much of the root system as you can. IF you leave too many roots behind the plant may die back somewhat to compensate.
Replant immediately at the same depth as they are growing now. When you prepare the new hole, loosen the soil over a wide area to encourage rooting, and also as deep as the rootball. Water them well the day before you dig and also water them thoroughly at planting time to eliminate air pockets. Mulch with several inches of organic mulch. Do not fertilize. They may defoliate due to transplant shock, this is a defensive mechanism plants use.
After replanting, water -- if needed -- to supplement rain so that the soil stays damp (not saturated, but moist like a wrung out sponge) until the ground freezes this fall. To know if you need to water, dig into the soil with your finger. If it is still damp, don't water yet. When you do water, water slowly and deeply to encourage deep rooting. After watering, wait a few hours and then dig down to see how far the water went -- sometimes it can be surprising. It is better to water deeply less often than to sprinkle lightly every day.
Next spring, you may see some winter dieback due to dehydration due to root loss. This can be trimmed off. Continue to water next summer, if needed, while they re-establish. Good luck with the move.
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