I have to move a rose bush and would like to know if it is likely to survive if I do that now. Obviously, I have to give it time to re-establish itself before the frost sets in here in Southern Ontario. For this reason, I don't want to wait until all the leaves fall off.
you'd really be better off waiting until early spring - just before it comes out of dormancy. if you need to do it now, do it on an overcast day and as early in the morning as possible. prepare the new spot by getting the hole dug and then dig up the bush. get a big root ball (wide and deep) so you're disturbing the roots as little as possible. when you put it in the new spot, water at the outskirts of the rootball so that the roots will reach out to the moisture (still do a bit on the main rootball, too. just focus a bit more further out so the roots will stretch out). and make sure you mulch really well so the roots are protected once the cold sets in. i just use crushed leaves about 6 inches worth or so.
Plants have ways that they function that are set in place before being handled and aren't always able to respond to attempts to manipulate them. Condition of plant fter re-planting and influence of seasonal conditions will have much greater bearing on what roots do than where you apply water afterward. If you are keen to get it done whack the top back below the level of foliage and move it. It being a rose chances are good this will not stop it. Or if you want to retain all the nutrients in the stems (these will be used to fuel new shoot and root growth at the appropriate time later) strip the leaves but don't cut it back much.
since this person wants to move it now and it's now close to getting very cold, doing something with the way it's watered to force the roots outward will help to get the bush re-established before it goes dormant. it'll have a better chance of surving the cold of winter if the roots are in good shape. sorry if i didn't make my thought clear enough.
I have been thinking about this and looking it up - I am with Ron on the root issue. My understanding is that the roots will grow in directions that it's been programmed to. Differential watering appears to influence the general direction of root growth. But this is not because the roots are going to preferentially grow in a specific direction, i.e., in the direction where there is more water, but it's because root growth in the direction where the soil is unhealthily dry is relatively poor. The plant ends up worse off, because the it is unable to reach it's full potential in terms of root mass. I.e. water evenly. I, myself, is a restless gardener, constantly splitting and moving plants, including roses. Unless it is a big specimen, I have not lost any roses from transplanting, even in summer. Given a choice, I would not move roses until October, and no later than May. If it's in the midst of the summer heat, I do it with the understanding that there is a risk that the rose will not make it. But as Ron suggested, the key is to reduce the foliage to cut down water loss from transpiration, but not to whack the rose so far back that you reduce it's ability to recover. I would water well, mulch and protect from full sun with some temporary shading if necessary. To me, the effort needed to pamper the plant is not worth it if I can put the move off another 2 or 3 months.
Cutting the canes too late in the season can force the plant to put out new shoot that don't have the time to harden before winter. I don't cut any canes when transplanting and wait untill the plant starts to show signs of new growth. Roses are hardy plants and the fear of death does wonders. If your really concerned about frost bury the whole plant over winter and replant in the spring.