It will look funny until the main canes that you are tying to the trellis grow lateral shoots out of them. This will fill in the gaps and that is what the blooms will be on.

I have climbing Sombreuil and it's a toughie. I wish mine would put out horizontal canes :) The good thing about roses is that they are always putting out new canes and you can train them easier than old ones.

The good thing about roses is that they are always putting out new canes and you can train them easier than old ones.

This is true!

Back when I was a teenager, in the 1970's, I inherited a 1950's book on growing roses (can't presently remember the authors' names, but they were serious rosarians). In that book there were three photos of a Harrison's Yellow rose (a beautiful early spring, once-blooming yellow shrub rose) they rehabilitated.

In the first picture it is a sprawling mess that has few flowers. In the second picture they tied all the main canes together and pegged them low to the ground, away from the crown of the bush, and consequently a whole new set of primary canes were shooting vertically from the bases of those old canes. In the third picture the old canes were gone and the new canes were blooming like crazy. It was obvious they had completely rejuvenated the bush by the simple technique of tying the old canes collectively to the ground and consequently stimulating the shrub to put out an entirely new set of major canes for them to work with.

The nice thing about a big rose is that as long as the growing conditions are to its liking you absolutely can rehabilitate it. Doing so requires a certain amount of sensitivity and expertise, but that can be learned.