Welcome to GoY, Ronalex!
About what part of the UK do you garden in? Planting times are very different between, say, Oxford and Edinburgh.

Definitely would not consider planting anything out up here in Moray, soil far too cold. As Tugb. has already asked 'where do you live in the UK?' Even if a lot further south by now the soil is likely to be cold and/or waterlogged.

Welcome from me too. As it is hard to give you advice without getting some answers to questions. I dk where you are in the UK but we have a hard ground frost in our area so any kind of planting is impossible. If you are concerned that the roses might get frosted if you do not plant them in the ground can I suggest you sink the pot in a much larger pot or alternatively replant them in a larger pot placed in a sheltered sunny site near the building (house). I thought you might like to look at the following link. http://www.vanmeuwen.com/how-to-grow-roses
Feel free to ask more questions on the subject using the add comment box so that we can all see how the conversation is going.