Question
I have 2 large (15-20 feet high) such roses, otherwise healthy and very leafy, but do not bloom.  I'm zone 7; one gets 3-4 hours of sun the other at least 6 hours; both growing through trees.  Thank you!

Answer
You didn't say how old your Lady Banks roses were. This is a rose that makes flower buds one year and then flowers on those buds the next year. If you prune this rose before it has bloomed, say in the spring, then you will have cut off many of the flowers. Another reason for not blooming, is that a cold spell in the spring has killed the flower buds.
The final reason is that this rose likes a lot of sun and perhaps 3 to 4 hours is not enough. If your roses have even bloomed once, then it will be the cold spring frost that has stopped the flowering.