I'd be willing to bet it's not the pH of your soil, but the chill hours in your climate. Just as there are stone fruit (apples, peaches, pears, etc.) and ornamentals (peonies, lilacs, etc.) which require "chill hours", there are also roses which require a threshold of cold to bloom. Many species roses and quite a few European Old Garden Roses require hours below forty degrees F to induce them to bloom.

Quite likely, where they grew in Colorado was much colder than where you live. My suggestion would be to dump ice around the crown of the plant several times this winter to 'fool' the rose into thinking it's had a harder, colder winter. This is precisely what you're doing when you store you tulip bulbs in the refrigerator or chilling your columbine seeds prior to planting to induce them to germinate or flower.

Until about WWII, most lilacs weren't suitable for milder winter areas, requiring fairly hard winter temperatures. Dr. Walter Lammerts developed and selected varieties which don't require that much chill and we now have the Descanso Lilacs, such as Lavender Lady, Angel White and California Rose which will bloom without harsh winter weather. Take a tip from the tulips and chill your R. arkansana plants with ice this winter. You'll probably have bloom this spring, IF you chill it long enough.