Since you plan to plant out your roses after starting them in pots, would think the type of soil you'll have in your garden at the new house is a key consideration. Will you establish beds at your new place with a blend of topsoil & compost or amend the native soil in some way to provide favorable growing conditions? In my experience, matching the container blend closely to the garden soil in which a plant will later grow is important, since a mismatch between the two can prove problematic down the line. Commercial "potting soil" substitutes peat moss as the growing medium for soil & is considered soilless. Plants growing in that can have a hard time expanding their roots into garden soil once transplanted & the original potting soil can continue to stay wetter or drier than surrounding soil for a good while until worms & soil organisms knit it into the whole. With your bare root roses, you'll mainly see anchor roots, as the finer network of feeder roots that grow from these are mostly lost in harvest & storage. Once planted, new feeder roots will develop from the anchors to multiply moisture & nutrient delivery. In a transitional pot intended for garden transplant, I like a slightly lighter version of the target site the plant will later occupy - a bit fluffier than the garden soil to maximize feeder root development & retard compaction of the planting mixture that can occur in a pot, but composed mainly of the same elements & textures of the final planting location, so a custom mix. When utilizing potting soil, I look for one with no fertilizer added or at most a slow release, but then I like to control what type of fertilizer & schedule, and generally give none to bare roots until they leaf out & in liquid organic form at that time to sidestep burning new feeder roots. Mixed thoroughly with quality topsoil & finished compost in equal parts, makes a good potting soil that can be further tweaked. Agree with nikthegreek about container size. Better to later pot up to a larger size if necessary when new roots have filled the pot than to have soil & roots fall away when you go to plant in the garden. Nursery pots are shaped to allow for easy transplant, can have the bottoms cut away, be supported beneath & placed in the planting hole & then have the pot sides cut way for minimal root disturbance. If using dark pots, slip them into light colored containers to keep them cool. Dark pots heat up quickly & can cook the roots. Potting bare roots this late, out of season, need to be careful the canes don't sunburn before leaf out, so the morning sun on your East facing porch should help until the foliage grows. If the humidity doesn't keep up, may want to mist the canes & new leaves with the mist setting of a watering wand to mimic moister air, or set the pots on large saucers filled with gravel & standing water below the top of the gravel which can evaporate moisture to the roses above. Have the impression your area is relatively low humidity usually? Turn the pots for leaf development as you would houseplants on a windowsill for even growth. Once they've leafed out, you may want to gradually give them more sun exposure till they get the same as where you plan to plant them. Most of the Austins here get morning sun from sunrise till 1-3 pm & do fine. If you find the growth stretching toward the sun even with turning the pots, that usually means they're wanting more of it. What an adventure for you - new roses, new home, new garden! Congratulations & enjoy the ride. (Just for the record, I'm in Nik's camp on rose potting for nourishment & endurance.)

Don gota go with fruitnut. We have planted lots and lots of bare root trees from Idaho, California and now Arizona. None- from a rep. dealer, mostly HD, Lowes, Wally world and 5 N dime. We have even planted them with lots of leaves still in their bags at the end of the season(April)because they where cheap. All soils in each place have been different acid in ID, great in Cali, crap in AZ. It really comes down to how they are planted and taken care of. It could be a water issue or soil issue. If your soil is really rotten like ours try a little root stimulater it may help.

Thanks - I'm just about to drill some holes in the plastic pots. I saw some advice on the container forum about using the 5-1-1 mixture of pine bark fines sphagnum peat and perlite but as they won't be in pots permanently I'll just use rose potting mix and put some perlite and peat moss in. An annoying thing we get here are curl curl grubs, they love living in pots and eating the roots. I found nearly 20 in a pot of rosemary that was looking sick.

adding topsoil and compost because have erosion issue. hoping once i plant it will help with this issue as well. I could just leave as is, but the truck will just dump it right where i need it, don't need to haul it at all! American holly is definitely one i will add too. I saw some large ERC Emerald Sentinel and they have an amazing fragrance as well. I do worry cultivars are not as good for wildlife as the straight species, but berries look the same. I will probably mix both to be safe. Loving the winterberry idea as well. BTW, is it true that Norway spruce is considered "invasive", as in it is replacing too many native species in Zone 7? Don't know if what I find in the literature sometimes is true or not... I will post pictures once I get started. Lots of great advice here,thanks!!