It depends on the rose, Ann. Most roses people grow for the big showy flowers are grafted. So a cutting will give you a less vigorous plant than the parent if you can get it to root.
So-called own root roses will grow true from a cutting because they are not grafted.
On the irises, you might be too late for this year. I am visiting in Utah (zone 6) today and all the tall bearded iris are in full bloom here. If you have nice neighbors with iris you could beg a few starts for next year if they are finished blooming.
