Many members of the rose society I belong to, grow roses in pots. They told me that it is eventually necessary to trim the rose roots and change the soil. If I remember correctly, they do this every four years, but the containers they use are huge. I think how often would depend on the size of the pot. This is why all my roses are in the ground. But they assure me that roses are tough and can take this treatment. I looked for a video that was specific to roses, but I found this one with a hibiscus and thought the same principles might apply. Hopefully someone who has trimmed rose roots can also respond. Best wishes for your root pruning project!

Here is a link that might be useful: Root trimming

Yes, containerized roses do need to be either potted up to larger pots or root pruned eventually. If you're at the largest sized pots you can handle then root pruning is the way to go.

Doing it during dormancy is probably the best time. Wait until just before they would normally start to come out of dormancy. Cut the tops down some both to make them easier to handle and also because you're reducing the amount of roots you have available to feed the top when they come out of dormancy. Take them out of the pots and shave the root ball down by about 1/3 (no more than half) and repot with fresh soil. When they wake up they should take off and start growing again and refilling those pots with roots, lol!

Why couldn't you prune the roots when you prune the tops of potted roses? That is precisely what they do when they harvest the plants from the growing fields prior to either sending them to you or storing them for shipment at bare root season. That's also what occurs when you transplant a rose from one spot to another, or remove it from the ground to be planted in a pot. The roots get pruned, and hopefully the tops, too, to keep them balanced so the plant has a greater chance of reestablishing itself and not dying from too extreme water stress. If you're receiving rains now, it's the perfect time to do the deed. You can pretty much get away with murder, figuratively speaking, when the rains keep the plants bathed in water after being so severely disturbed. Good luck! Kim