From experience, I have learnt it is better to be safe than sorry!
My standard roses in manageable pots get move into our unheated storeroom. The bigger pots get wrapped and the roses themselves treated the same way as the standards planted in the garden. First I stuff the crown with wood straw and then double wrap with winter 'vlies' (sorry don't know the correct term in English). It is a light weight winterizing fabric alternative to burlap. I then mound the base.
I posted this pic before in the 'Rose Tree?' started in July.
Another thing you might want to do before wrapping up your roses is to remove all the leaves and spray them with dormant spray first.
Hope that helps
