overwintering roses in zone 5a

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Hi I just finished planting my rose garden and was wondering if any of you near my hardines zone (or colder) have any tips on overwintering. I have had two roses that have lasted 2 winters with no protection. They arent the hardy roses, but they arent hybrid teas either (lost their tags... ermm... thre away their tags ). Anyways, I added four more roses to my rose garden this year, and want to make sure that they live

I bought: (they can go down to the listed temp)
-Grandiflora 'Tourament of Roses'-17.7 °C (0 °F)
-Grandiflora 'Pink Parfait' -28.8 °C (-20 °F)
-Hybrid Tea 'Mister Lincoln' -17.7 °C (0 °F)
-Hybrid Tea 'Neptune' (Zone 6b) -17.7 °C (0 °F)

oh.. I guess I don;t need to worry about pink parfait... she'll survive fine

I plan on saving a bag of earth for each plant, and will mound it over the plant in the fall. Then I want to put one of those styrofoam 'things' on top of each.

Do you think they will live? I mean they sold the plants at my local garnden center, and I assumed they could survive this climate.

Thanks!!