Your tub is rather small for the plant height that you would like to achieve. Roses have deep roots so your tub would need to be at least 80 cm tall to be suitable. The roses would also need to be planted in loam-rich or clay-rich rose compost. In addition, it is likely that the partial shade would limit your rose's ability to produce flowers.
As small tubs like the one you mentioned freeze over completely in winter, a shady location is a challenge for virtually all perennials planted in containers of this type. How about using this tub to plant annual climbing plants like cup and saucer vines, Chilean glory flowers, morning glories, sweet peas, runner beans, purple bell vines or black-eyed Susans? With sufficient fertiliser and water, you will then have a beautifully planted tub all summer long (perhaps with some underplanting around the climbers) — and no work to do in winter.