Moving a rose bush

Whereabouts in the country do you live, ExDancer? if you’ve had prolonged drought like a lot of us I would wait until autumn - even though you are transferring it from a pot.

Give it a good prune and don’t plant it in soil where any roses have already been grown and enrich the soil with rose fertiliser or a general purpose organic one.

So long as you water regularly until established it should be fine and will love it’s new position.

As it is in a pot there will be very little root disturbance so I would be happy to move it anytime except perhaps in a heatwave.
I always puddle in plants. So dig a huge hole, add lots of organic matter from your compost heap or bought in, fill the hole with water and allow it to drain into the soil, refill the hole with water pop in the well watered plant and fill round about it with mixed soil and organic matter, water once a week for the first year if there's little rain.

I’d leave it for a few weeks, unless you’re in a desperate rush to get it into the ground. The problem at the moment is that the ground is bone dry, so even if you water it in thoroughly the water will just leach away. You’ve got a better chance if you leave it until mid to late September, when the soil will still be warm but hopefully a lot wetter.

I think you can plant out a shrub grown in a pot at any time.

I'd pour plenty of rainwater (if you have any saved) into the planting hole so the roots will go down, because it's been so dry lately, and mulch it too.

If you're moving shrubs from one area to another that does need to be done in the winter, November to no later than March so they establish their roots.

I always puddle in plants
Yes, that's the term I was looking for.

I always puddle them in too.

You can, but I wouldn’t. This is what it says on David Austen Roses:

‘Potted roses can be planted all year round. The only time we recommend that you don't plant is when the ground is frozen, waterlogged or in drought conditions.’

I’ve been gardening today, and where I am the ground is bone dry still, so I wouldn’t risk it.

This is a lovely old Bourbon type rose with pink petals and no thorns - first hybridised circa 1860 .
It's not cheap to replace so don't risk planting it out now !
I don't plant roses in the summer and not in a drought .
November is the best month , but not if the ground is frozen .
October would be okay .

Prepare an area in which roses have not been grown before or the soil will be rose sick .
Choose an area which is not overshadowed by trees and shrubs so that rainwater doesn't drop on it .

Prepare the ground very well by double digging and use well rotted farmyard manure .

Dig a nice big hole and gently tease out the roots which might be slightly pot bound .
If any are damaged you can cut them off with sterilised secateurs .

Use a garden cane to establish the depth by laying it across the hole
The soil needs to reach the junction of the rootstock and cultivar.
You'll see it easily - there will be a scar indicating the graph .

Water well and mulch .

I'd use a slow release fertiliser certainly by the Spring when the first shoots show .

And enjoy !

AFAIK it’s always best to wait until we’re well into autumn before transplanting any shrub. That way they have time to get roots well established before the start of new spring growth. Plus of course plenty of water if there’s a dry spell.,

They are much easier to handle while the soil is dry and can be moved at any time. Cut the stems right down to a few buds and then move it. Pop it into a prepared hole with some rich damp organic compost. Water it and just watch the buds start to grow within days. You don`t need to go over the top re prep at all and it will live on

@ExDancer
By coincidence I've just moved my Zephirine Drouhin as well! Yours should be fine as it's in a container so can be planted out at any time, and I agree with the advice given so far. Mine was in the ground and sadly I had to move it while still in leaf but I took cuttings just in case. It's such a lovely rose and has thrived in the garden for twenty years despite long periods of neglect. Lovely for a garden where children are playing as there are no thorns. I'm sure yours will love being in the ground!