I have a deep purple jackmani with one, its spectacular. Over the years, the clematis has completely overwhelmed the rose, I planted them side by side. That could be controlled by planting them further apart, say 3 to 5 ' apart, and then guiding a dozen strands of the vine over.

Thanks. Sounds like a good combo. It does need something strong enough to stand up to the color. Maybe I'll look for a smaller variety of that purple. The jackmanii is so vigorous I'll be wrestling with it every year!!!

these might not answer your questions, but this is a forum
The parsly one may help with the roses smell though.
I read that parsly around base of a rose Increases Fragrance(also will repel rose beatle whatever that is.

helps
Chive (Allium schoenoprassum) black spot on roses, fruit tree insect

GARLIC: Plant near roses to repel aphids. Accumulates sulfur: a
naturally occurring fungicide which will help in the garden with
disease prevention.

I have a roguchi (Sp?) clematis that is a deep blue violet, but the blooms are shaped like a blueberry blossom and it isn't as vigorous for me as Jackmanii. The bells are about 2 inches square. I have it with Fourth of July roses.