You may want to try a vining clematis on each pillar. They are excellent companion plants for roses. Clematis can be planted next to your roses and will grow up and through the roses.
Good Luck.

Most climbing plants need something to climb up, and pillars by themselves don't do the job as they're too big. Climbers come in four basic varieties: those that hold by twining, by suction-like roots, by tendrils, or just by ranging upwards and hoping for the best. To work in a garden setting, all climbers need some direction and support.

Your roses fall into the latter category and you would need to take the tallest canes and tie them to the pillars, and support them continually until they are where you want and forever afterward. Pruning is also involved to control bushiness at the base and stray branches that block the entrance.

To grow the other types, you can maybe screw a number of hooks into the pillar (top and bottom) and run twine between them and across the top of the porch for either twiners (like Stauntonia) or tendril climbers (most clematis) to make it up high. The suction cup climbers (flowering hydrangea) might hold onto the pillars, but they might also damage it.

You might enjoy reading some books on growing climbing plants - there are many available, some better than others. But all will give you a foothold in the topic - which is basically what your climbing plants need!

Best of luck; I enjoy the enterprising can-do spirit with which you undertake your projects.

KarinL