Iceberg Floribunda Rose
I think this is an Iceberg Floribunda Rose [Rosa Iceberg (‘Korbin’) rose Iceberg (bush floribunda)] – at least that’s what I bought it as. It has been growing since about 2000 and flowers profusely over the summer months with a perfect rose fragrance. It’s making a grand last stand for blossoming. It’s buds appear as a gentle pink and explode the next day into these bleached-white voluptuous petticoats of roses. They are short-lived as individuals, but there are so many and for so long, it seems to be ever blooming during the summer. It has wicked thorns and will spread if allowed. I have it planted with a red weigela and it is quite beautiful when both bloom simultaneously. Iceberg Floribunda is described as disease resistant – although, the Japanese beetles do like it – and hardy to grow in MN.
Growing in Zone 4 
I think the rose you have is a rugosa type shrub variety called ‘Snow Pavement.’ Google images of it and also of ‘Iceberg’ to note the different type of leaf and petals. ‘Iceberg’ is a floribunda with dark glossy leathery leaves. Both are lovely!
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You are very observant and I think you’re correct!
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