Hi Carolyn,
I've lived in zone 6b and I planted bare root roses in late March or early April. I now live in zone 7b and I plant bare root roses in March. I got some from SW greenhouse at the beginning of March this year. My Palatine order arrives mid March. A Pickering order will arrive end of March. I can attest to the fact that May and June are right out. The roses will all die before they get established. Probably all of them. That said, I think even dormant bare root roses resent too many freeze-thaw cycles, so at least where I live here mid February is too early. I planted a shipment of Palatine roses at the beginning of April last year and they all survived until frost, so I bet you could plant until April 15th if you were careful to keep them very well watered as they establish.
Potted roses are a different matter. Many will survive light frosts, but if the temperature drops enough for the leaves to be destroyed - perhaps mid or low twenties - it can destroy the plant. So I usually wait to plant those at least until mid April. I took a shipment last April 21st of nice, leafed out roses from Rogue Valley Roses. A storm blew in on the 23rd when most of the roses were in the ground, taking the temperature into the teens. I lost all that I had planted. Very disappointing.
Good Luck
