Posted: 16/02/2013 at 17:53
The simple answer is yes you can.
The longer answer is tie in the new shoots in a back (then forth motion- as it grows). Your next issue is the type of arch you have, some roses don't get too heavy until after a few years but if you trim back the unwanted weight you should be able to cope. I had one last year that had only previously grown by about 1ft, then I put in a cheap arch, and it grew over 8 ft in 1 year, needless to say, I pruned it back in November and re-tied it to the support, as it now grows I will train the new growth over the support.