I'm not familiar with the first rose you mentioned, or it's growth habit and pattern, but they do look amazing for having been grown in pots ! You're also most likely correct that they've rooted into the soil below the pots by now, so I wouldn't disturb them. Just continue to water them and feed them.
Some climbers do tend to have concentrated growth at the top of the arbors and bare canes down at the base.
I don't know how often you prune yours, but a considerable thinning out of the top of the plants and then giving them some Epsom salts may very well encourage new basal growth as well as lateral growth from those older canes. I've encountered that problem in the past and the thinning/epsom salt treatment worked well.
Another thing you could consider doing (if the first suggestion doesn't work) is a remedy I tried and was successful with:
I planted a much shorter and less vigorous climber at the base of the big one which eventually "hid" the canes of the older one. You could also plant a smaller more manageable flowering (or green) vine at the base to get the same effect...i.e. clematis or some sort of climbing annual. I've used the shorter varieties of sweet peas to achieve that effect...ones that only grow to a max of about 5'.
