Sorry, I forgot to mention that these roses are approx' 2-3 years old.

Yes, do worry about transplant shock, but when roses need to be moved we have to make the best of it. Plants are still young and are full of life. Transplanting often works out fine even in less than ideal circumstances.

1. get as much soil as possible around the root ball

2. keep the soil wet and do not let them dry out.

3. protect them from the harshest sun with a fiber cloth or something like that. They are usually available in the garden center, with half circle wire support to make a tent-like construction. From the right seller they don't cost much. Failing that you can improvise with the cloth.

4. Having planting holes ready in advance will help protect the plants from drying, or just pot them up for a while.

5. Keep soil moist and spray plants if needed. If you have water soluble seaweed extract it can help roots to recover.

I live in a very different climate than you, and my family have a house in south of France where the sun can get pretty hot too. Still they manage to move roses and other plants if needed during summer. There we hope for rain and cloudy weather.

Best of luck :-)

As taoseeker points out, drying out is the biggest danger. Have your new holes or pots ready to receive the transplants. If you can choose an overcast day, that's best. Or do it in the evening when it is cooler. If they are large or have lots of small growth, you might want to prune them down some a few days before digging.