I lost four bushes last winter. I have two that are almost dead - one measly sprout that is short and not doing much. How can I nurture these or do I just need to replace them?

Pictures of your roses would greatly help answer your question.

are the roses hardy to your zone 5? Do you cover or mulch them in the winter for protection?

Hello Margy,
Pictures would really help to guide our advice to you.
Also a little more info on the actual plts.
Are they H.T.s, grafted?
And as Ashley asked how did you winterize them?
Remember, if you do decide to replace them, many here can help you to get the best type for you and your zone.