I am a Rosarian with at least 30 years growing roses, so here is my advise for transplanting your miniature roses to one location.
This is the how you should proceed.
The roses should be transplanted while they are dormant. That could be late winter or early spring. You should wait until all danger of frost is gone and the ground is workable.
Before you dig up your mini roses, prepare the new bed several days before moving your roses.
Soil preparation is the key to healthy roses.
Good drainage is critical, because roses do not like wet feet, meaning the soil should drain properly. The best way to accomplish this is the build up the bed about 8-12 inches.
If the soil in your new rose bed drains adequately, till or dig the soil to a depth of at least 1 foot.
Thouroughly mix in 6-8 inches of compost (composted cow or horse manure is the best, available at garden centers) and a cup or two of alfalfa meal, and bone meal, according to package instruction.
Water the bed deeply, and let it settle for a few days. A week is OK.
Now is the time to dig up your mini roses. This is best done on an overcast or misty day.
When you dig up your roses, care needs to be taken to lessen the transplant chock.
Using your shovel, dig, a foot to 18 inches, around each plant and immediately protect the root ball by wrapping it with damp burlap or platic sheeting.
Dig holes for each rose in your new bed. Dig a hole that is twice the diameter of the rootball, but not less than 18 inces wide and 12 inces deep. Mix a cup of compost with your prepared garden soil in a bucket.Position the plant carefully in the hole. Use a stick across the planting hole to check that the bud union is at the desired depth. In your cold region the bud union should be 1-2 inches below soil level. Fill the hole around the rose with the prepared soil in the bucket. Water the soil as you fill the hole to eliminate any air pockets. Tamp the soil down loosely, be gentle with the roots.
With a hose deliver a good, slow soaking to the newly planted roses. This eases the roots' transition into the hole and eliminates any air pockets.
If watering causes the rose to settle too deeply, just grasp the main stem and tug it gently back up to the proper spot, let go and se if that does the trick. If it doesn't settle higher, you may not have backfilled enough soil into the hole. Carefully remove the plant from the hole and try again.
But by reading this before planting, you will most likely avoid this problem.
Now , there is one more thing you should do before transplanting the roses. When you have dug up the roses and before you transplant them, trim off any dead and/or diseased looking canes. Also remove any spindly and criss-crossed canes.
Carefully shorten any roots that are extremely long or broken.
There is a product available at the garden centers for help with transplant shock. I advise you to buy this product. Ask the staff to recommend one that they would use.
Carefully read the instructions and apply at planting time.
Your roses should be watered daily until established.
When you see buds to begin to swell later in the spring, it's time to take out the pruning shears.
Because they are short to begin with, you don't want to prune to zealously.
Prune to shape lightly in the spring, shortening strong growth to keep the plants in bounds.
Cut out old stems after a few years.
Now apply about 3- 4 inches of a good quality mulch around your roses ,or better yet, if the bed is small, cover the bed with this mulch.
This mulch will break down and add nutrients to the soil. When you see it disappearing, it's time to apply another layer of mulch and so on.
When new growth starts to appear it's time to apply som organic fertilizers like fish emulshion or liquid seeweed. Read instructions carefully so you do not burn the roses.
Good luck with your transplanting.
Please visit my Web Site for more information on growing roses and beautiful pictures of my favoritte fragrant roses.