Opinions differ, which usually means you are fine doing it either way.

I deadhead until the rose-stopping frost, because I know of no evidence that not deadheading increases winter hardiness.

I fertilize (moderately) until around October 1, because I know of no evidence that not fertilizing increases winter hardiness. I stop around October 1 because the fertilizers I use will then run out about the time of the rose-stopping freeze.

Under this regime, I get good late-season bloom and the garden looks neater, while my roses will be cane-hardy at our likely winter low of 5 degrees. Of course, whether you deadhead and fertilize or not, you will lose any soft new growth that is on the roses in November

I could not agree more with Michaelg's comments. Do the same here in SE Michigan.

When you get fed up doing it.
Honestly, not being facetious..... there is definitely a point, every year, where I think, OK, that's enough for now, I am bored with it.....and that time always seems to happen as we naturally move out of summer and into autumn......which I also regard as the start of the gardening year and there is a whole heap of new stuff to get on with (sowing, digging, dividing, bulb planting, pruning, bare roots, planning). So, if, as it seems, it is not so shatteringly important to follow strict timetables, maybe please yourself.

I fertilize and deadhead right up to when they go dormant. Whether you leave the hips or not the rose will continue to grow until it gets too cold and there isn't enough sunlight for them to continue growing and it finally goes dormant. I prefer mine to go into winter healthy, well fed and watered so they will have lots of stored energy to come back with in the spring. In your zone you probably don't get a great deal of winter die back anyway so I would continue your regular routine until they've gone into dormancy. In my zone I get more die back but I've never seen much difference in the amount of that die back whether I dead head or fertilize or not going into fall. The roses will just go on growing until it gets too cold and if they're not fed they'll use stored energy to do it leaving less for spring.

I guess, if I was being conscientious, I would step on the potassium more than nitrogen or phosphorous....we were always taught potassium was good for hardening woody growth for winter. Probably be more reticent with the nitrogen though.....although, it frequently depends what's left in the shed at this time of year, also.

I dead head till there are no more old dead blooms to remove and fertilize till I no longer feel like doing it which is usually October.