If you're feeding readily available chemical fertilizers, then 6 weeks before the first hard freeze (different and later than the first frost date) should be about right. For someone feeding organics that need soil microbial activity to happen in order to make the nutrients available to the rose, then about 3 weeks earlier than that date should be about right.

I usually apply my last at the end of August/beginning of September, and it's a water-soluble (soil drench). Last application of granular/organics (Mills Mix or Rose Tone) is the beginning of August.

Thanks guys, very helpful.

No more fertlizer for my roses this year.

If you applied organic fertilizers in the spring or summer, there will still be a good deal of nitrogen in the soil in fall, but as the soil cools, bacteria are less active in converting organic nitrogen to soluble, usable forms. So available nitrogen declines automatically, but there will still be some present. Most of the remaining insoluble nitrogen will carry over to the next season or two, so we can fertilize about 1/3 less in succeeding years compared to what was needed the first year.