If its a standard, its grafted at the top of the stem, and what's been grafted to it is critical from a pruning point of view. If its got a rambler grafted to it, that should be done in September - if its an HT or floribunda, they get pruned properly last week of February, though you can remove some long growths now to prevent wind rock over winter. When you do prune, remember that you must not cut beyond the graft point at the top of the stem.