A few points:

Most of Puget Sound is USDA 8.

8 ft tall is not enough for a truly vigorous rose, there are many that would outgrow your space - watch that you do not plant a 20+ footer because you looked for "vigorous". For instance, 'Climbing Cecile Brunner' is prevalent and easy here, but I have seen that up a utility pole and above the uppermost set of wires.

You could, of course prune to control size - if so inclined. There is a 'Climbing Cecile Brunner' near me that is sheared to form a tight arch over a door-sized gap used for access through a sheared laurel hedge. It manages to bloom well despite being almost a topiary.

Other ones seen to be pretty much carefree here include 'Alberic Barbier', 'Aloha', "Darlow's Enigma" and 'Madame Alred Carriere'. All of these except the second will try to bulge out of the area you have available, have to be pruned back at some point. The third makes prickles like fish hooks during the early years, when twiggy but appears essentially impervious to disease in this region. The last may show some mildew during the right conditions for it during summer (dry roots + dewy nights). With consistent, effective watering you may see little of it.

Oh yes, I tried Zepherin D and cut it down and removed it after a few years. NO fragrance, ugly flowers, and horribly diseased.

Really, you don't think 8, may actually be 9, 4 feet deep and 12 feet long would be enough room for a vigorous grower? That's about 20 feet for it to grow, or at least that is my hope, to have it grow that length. Thank you so so much for your recommendations though! Good feedback on the prickles. The arbor is huge and very sturdy, we built it of cedar a few years ago, and from the bench, standing, I can barely reach the trellis portion with my hands. I'm hoping to find something that will provide a bit of shade while sitting. Perhaps I will contact the Tacoma rose society directly. I had seen that they recommended fourth of July and a few others, have you ever seen it in action?

Rose societies tend to be focused on large-flowered modern types that lend themselves to exhibition - and not too concerned about having to spray. This is a generalization, of course, but I have looked at local recommended roses lists for years and gotten that impression.

Rather than being particularly vigorous 20 ft. tall is kind of in the mid-range for climbing and rambling roses. There are roses present in this region that are triple that height. When furnishing a limited space (as opposed to a large tree or other area effectively without boundaries) you really need to be mindful of likely size expectations for climbing plants chosen. Before I decided to change the planting it was in, discovered the rose had picked up (ugh!) crown gall an 'Alberic Barbier' here had rambled 20 ft through neighboring shrubs.

If you want a real CLIMBER try Rambling Rector.... but only blooms once in the season, white and very vigorous. My favourite climber (again, totally rampant,) is Island Pearl, developed on Bowen Island. Lovely clusters of pink/white flowers in masses, but again, only booms once in the season. Will be 20ft or more by the third season!