Finche,
I plant iris in the fall. Most of my iris bloom in the fall and the spring.
Daylillies you can plant in fall, they may not bloom, but your suppose to plant them in fall.
Buy yourself a Seven SOns flowering bush online somewhere, they will bloom the entire fall, and they have beautiful fragrant flowers. I have one and when it blooms, everything else is done. Very hardy bush too, amazing.
Roses bloom at a peak in the fall. You should really plant them in the spring though, they need the summer to root in in your zone.
Pansies are very cold hardy and they will reseed for you in the spring. I love pansies.

Generally you plant bulbs in the fall. Iris is good too. Daylilies can go in anytime there is no frost.

Plant peonies. Autumn is the best time and they will do well in your Zone 5. You can order divisions online from nurseries. They are planted in September and October, generally. Peonies are deer proof as they have phenol compounds in the plants that make them taste bitter. We started with roses and quickly gave-up on that battle as we have deer and rabbits. Peonies LOVE hillsides and good drainage, growing native on the sides of mountains and hillsides in Asia. I have over 100 varieties and get blooms for six to eight weeks. Day lilies are also good on hillsides and bloom after peonies. Daffodils and tulips, also. But, deer love daffs, day lilies, and tulips. As a rule, those flowering plants that bloom in the Spring are planted in the Fall, and vice versa. Let me know what you think. Steve

I am very happy with the yarrow that I planted last fall and it is blooming well this year. I also planted cardinal flowers which are blooming now. Anise hyssop is blooming now and it attracts a lot of bees and butterflies. Weigela blooms in the spring but reblooms in August. Black eyed susans are out now and Autumn Joy Sedum is just starting.