Um, not sure really. Climbing hydrangea petiolaris doesn't really act like a climbing rose - it is a wall or fence coverer with a lot of short lateral growths which really cover a surface in a sort of 2dimensional growing mode...and also has vigorous adventitious roots which may not play well with a rose. I might be tempted to try a less vigorous and flexible climber on top of an established hydrangea but on the whole, would be more inclined to stick with a clematis viticella type if I really had to grow 2 plants together.

Evergreen hydrangeas (serratifolia and seemannii) are a bit more iffy, even in Z8, so have only grown the deciduous petiolaris as well as schizophragma integrifolia.