The best treatment for roses is a specialist rose food such as Toprose and/or composted manure - but either way, its too late in the year now. What you can do is mulch them now with composted manure, they'll love that for next year. Toprose and the like should be applied in April and then in June, you can use Growmore if you like, but it doesn't have the trace elements in it - if you do use Growmore, a handful or three around the base of the roses, raked or turned in, in April and again in early June.

Thank you Bamboo I will take your advise.

I generally put chicken manure pellets round my roses in Spring and they seem to do very well. As do clematis.

Thank you.