A lot of climbing roses love to be pruned in the Fall: After the first frost and the leaves have fallen, you can really see what you're doing.  And it's cool enough to wear a heavy shirt and gloves, so thorny rose canes are less likely to draw blood as you sort through them, choosing which to prune off and which to tie-in.

Sander's White is a giant, getting twenty feet tall and wide if you can train it up and out that far.  So pruning it is a big project too.  Rest up and bring coffee:  You'll need both if you're going to get done in a day.